AP Inter 2nd Year

AP Intermediate 2nd Year English Textbook Solutions

AP Board Solutions Class 12 English

English Inter 2nd Year Unit 1 Roots

1. Kindly Adjust to Our English Questions and Answers (Prose)
2. Once Upon a Time Questions and Answers (Poem)

English Material 2nd Year Unit 2 Confession

1. I Am Sorry The Three Hardest Words To Say Questions and Answers (Prose)
2. My Vocation Questions and Answers (Poem)

English 2nd Year Material Unit 3 War and Peace

1. I Have a Dream Questions and Answers (Prose)
2. Hiroshima Child Questions and Answers (Poem)

Inter 2nd Year English Textbook Answers Unit 4

1. The Hound of The Baskervilles Questions and Answers (Non-Detailed Text)

AP Inter 2nd Year English Grammar with Answers

English Grammar Inter 2nd Year
Study and Communication Skills

• Conversation Practice (Dialogue Writing)
• Letter Writing
• Cloze Test
• Reading Comprehension (Unseen Passages)
• Reading Comprehension (Non-Detailed)
• Interpretation of Non-Verbal Information
• One Word Substitution
• Note Making
• Resume Writing
• Form Filling a Life Skill
• Idioms and Phrases
• Word Stress
• Language of Advertisements

AP Inter 2nd Year English Weightage BluePrint 2026-2027

AP Inter 2nd Year Study Material

Reviewing AP Inter 2nd Year Zoology Study Material Chapter 4 Molecular Basis of Inheritance Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Zoology 4th Lesson Molecular Basis of Inheritance Questions and Answers

IV. Very Short Answer Questions

Question 1.
What are VNTRs?
Answer:

1. VNTRs (Variable Number of Tandem Repeats) are DNA sequences that act as important genetic markers.
2. The number of VNTR repeats differs among individuals, making them useful in DNA fingerprinting.

Question 2.
List out any two applications of DNA fingerprinting technology.
Answer:
Applications of DNA Fingerprinting:

1. Forensic investigations
2. Medico-legal cases
3. Pedigree analysis

Question 3.
What is DNA polymorphism?
Answer:

1. DNA polymorphism refers to genetic variation caused by mutations.
2. When an inheritable mutation occurs frequently within a population, it is termed DNA polymorphism.

V. Short Answer Questions

Question 1.
Write the salient features of the Human Genome Project (HGP).
Answer:
Important Features of the Human Genome Project:

1. The human genome is composed of chromosomes containing nearly three billion nucleotide base pairs.
2. An average human gene contains about 3000 base pairs, although gene sizes vary greatly. The largest known gene codes for dystrophin.
3. The total number of genes in humans is estimated to be around 30,000, and about 99.9% of
   nucleotide sequences are identical among all humans.
4. The functions of nearly 50% of the identified genes are still unknown.
5. Less than 2% of the genome is involved in coding proteins.
6. A major portion of the genome consists of repetitive DNA sequences.
7. These repetitive sequences may not have direct coding functions but are important for understanding chromosome evolution and dynamics.
8. Chromosome 1 contains the highest number of genes (2968), whereas the Y chromosome contains the fewest (231).
9. Around 1.4 million SNPs (Single Nucleotide Polymorphisms) occur in humans and help in disease mapping and evolutionary studies.

Question 2.
Describe the steps involved in DNA fingerprinting technology.
Answer:
DNA Fingerprinting-Procedure:

1. Collection of DNA: DNA is isolated from sources such as blood, saliva, semen, hair roots, or tissues. If needed, DNA is amplified using cloning techniques or PCR.
2. Fragmentation of DNA: DNA is cut into smaller fragments at specific locations using restriction endonucleases.
3. Separation of DNA Fragments: The DNA fragments are separated by agarose gel electrophoresis. Smaller fragments move faster and travel farther through the gel.
4. Denaturation: The double-stranded DNA is converted into single strands using heat or alkaline chemicals.
5. Blotting: DNA fragments are transferred from the gel onto a nylon membrane. This transfer process is known as Southern blotting.
6. Hybridization with DNA Probes: Radioactively labelled DNA probes complementary to the target sequences are added. These probes bind to matching DNA fragments.
7. Probe Hybridization: After binding occurs, excess probes are removed, leaving only DNA- probe hybrids on the membrane.
8. Autoradiography and DNA Fingerprint Formation: The membrane exposed to photographic film. Radioactive signals produce characteristic bands that form the individual’s DNA fingerprint.

VI. Long Answer Questions

Question 1.
Why is the Human Genome Project called a mega project?
Answer:
The Human Genome Project (HGP) is regarded as a mega project because of its enormous scope, high expenditure, long duration, and the vast amount of genetic information it generated. It demanded worldwide cooperation, significant financial support, and sophisticated computational technologies.

The following points explain why it is considered a mega project:
1. Huge Number of Base Pairs: The human genome consists of nearly 3 × 10⁹ base pairs, making it extremely large and complex. Identifying and sequencing every base pair across all chromosomes was an enormous scientific challenge unlike any previous genetic research.

2. Enormous Financial Investment: The project required substantial funding. If sequencing a single base pair cost about $3, the estimated expenditure for the entire project would have been approximately $9 billion. Such an extraordinary financial commitment makes it a true mega project.

3. Extended Time Period: Completing a project of this scale required careful planning and many years of work. Initiated in 1990, the Human Genome Project was successfully completed in 2003, taking nearly 13 years.

4. Massive Data Generation and Bioinformatics: The project produced an enormous volume of genetic data. If this information were printed, assuming each book contained 1,000 pages with 1,000 letters per page, nearly 3,300 books would be needed to store the genetic information from a single human cell. Managing, storing, and analyzing such data required advanced computer systems, leading to the development of the field of Bioinformatics.

5. Global and Multidisciplinary Collaboration: A project of this magnitude could not be accomplished by a single nation or institution. It involved international cooperation under the coordination of the U.S. Department of Energy and the National Institutes of Health (NIH), with major contributions from the United Kingdom, Japan, France, Germany, and China. Scientists from diverse fields, including biology, computer science, engineering, and mathematics, worked together to achieve its objectives.

6. Significant Scientific and Medical Impact: The Human Genome Project revolutionized biological and medical research. It enabled scientists to identify the genetic basis of numerous diseases, improved preventive healthcare, and supported the development of personalized medicine and pharmacogenomics, greatly benefiting human health and scientific advancement.

Question 2.
Write an essay on DNA Fingerprinting.
Answer:
1. DNA Fingerprinting: DNA fingerprinting is a technique used to identify individuals based on the unique pattern of their DNA. Since every person (except identical twins) possesses a distinct DNA profile, this method is highly reliable for identification.

• DNA fingerprinting is also referred to as DNA typing or genetic fingerprinting.
• It is extensively used in forensic investigations, paternity and maternity testing, and individual identification.
• DNA samples can be collected from blood, saliva, semen, hair roots, tissues, bones, or other biological materials.
• Although more than 99% of the nearly 3 billion base pairs in human DNA are identical, the remaining variations make each individual unique.
• Except for identical twins, no two individuals possess the same DNA sequence.
• These variable DNA regions are known as Restriction Fragment Length Polymorphisms (RFLPs) or Variable Number Tandem Repeats (VNTRs).
• The pattern of VNTRs differs from one individual to another, making them useful for identification.
• The DNA fingerprinting technique was developed by Sir Alec Jeffreys while studying the myoglobin gene.

2. Procedure of DNA Fingerprinting. DNA fingerprinting involves the following steps:

Isolation of DNA: DNA is extracted from biological samples such as blood, saliva, semen, hair roots, or tissues. If required, the extracted DNA is amplified using cloning or DNA amplification techniques.

Digestion of DNA: The isolated DNA is cut into smaller fragments at specific recognition sites using restriction endonuclease enzymes.

Separation of DNA Fragments by Gel Electrophoresis: The DNA fragments are loaded onto an agarose gel and subjected to an electric field. Smaller DNA fragments migrate faster and travel farther through the gel than larger fragments.

Denaturation of DNA: The double-stranded DNA is separated into single strands using alkaline chemicals or by heating.

Southern Blotting: The separated DNA fragments are transferred from the gel onto a nylon membrane by placing the membrane over the gel and allowing absorbent paper to draw the DNA onto it. This transfer process is known as Southern blotting.

Identification Using DNA Probes: Radioactively labelled DNA probes, which are complementary to specific DNA sequences, are added. These probes bind to the matching DNA fragments through hydrogen bonding.

3. Hybridisation with DNA Probe: After hybridisation, the excess probes are washed away. The nylon membrane containing the DNA-probe hybrids is then covered with photographic (X-ray) film.

4. Development of the DNA Fingerprint: The radioactive probes expose the photographic film, producing dark bands that correspond to specific DNA fragments. The unique arrangement of these bands forms the DNA fingerprint of an individual.

5. Applications of DNA Fingerprinting :

• Forensic Science: Used to identify criminals and establish the identity of suspects.
• Medico-Legal Cases: Helps determine biological relationships such as paternity and maternity.
• Anthropological Research: Assists in studying human evolution, ancestry, and migration patterns.
• Pedigree Analysis: Used to trace inheritance patterns across generations.
• Taxonomy: Helps in studying phylogenetic relationships among organisms.
• Wildlife Conservation: Assists in maintaining genetic records and conserving endangered species.

I. Multiple Choice Questions

Question 1.
Which chromosome in the human genome has the highest number of genes?
1. Chromosome 1
2. Chromosome 10
3. Chromosome X
4. Chromosome Y
Answer:
1. Chromosome 1

Question 2.
Expressed Sequence Tags (ESTs) refer to.
1. Novel DNA sequences
2. Genes expressed as RNA
3. Variable Number of Tandem Repeats
4. DNA polymorphism
Answer:
2. Genes expressed as RNA

Question 3.
DNA polymorphism forms the basis of
1. Genetic mapping
2. DNA fingerprinting
3. Both genetic mapping and DNA fingerprinting
4. Translation
Answer:
3. Both genetic mapping and DNA fingerprinting

Question 4.
Match the following List – I with List-II with reference to salient features of Human Genome.

Choose the correct answer from the options given below.
1. a-ii, b-iii, c-i, d-iv
2. a-ii, b-i, c-iv, d-ii
3. a-iii, b-i, c-ii, d-iv
4. a-i, b-iv, c-ii, d-iii
Answer:
3. a-iii, b-i, c-ii, d-iv

Question 5.
The largest known human gene is located on
1. Chromosome 1
2. Chromosome X
3. Chromosome 2
4. Chromosome 21
Answer:
2. Chromosome X

Question 6.
Given below are two statements. One labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): Mutations in non – coding DNA sequences keep on accumulating generation after generation and form one of the basis of variability/ polymorphism.
Reason (R): Mutations in non – coding DNA sequences may not have any immediate effect/impact in an individual’s reproductive ability.
In the light of above statements, choose the most appropriate answer from the options
given below.
1. Both A and R are correct, and R is the correct explanation of A.
2. Both A and R are correct, but R is not the correct explanation of A.
3. A is not correct, but R is correct.
4. A is correct, but R is not correct.
Answer:
1. Both A and R are correct, and R is the correct explanation of A.

Question 7.
Given below are two statements.
Statement I: DNA fingerprinting is the basis of paternity testing in case of disputes.
Statement II: DNA polymorphisms are inheritable from parents to children.
In the light of above statements, choose the most appropriate answer from the options given below.
1. Both statement I and statement II are true.
2. Statement I is false, but statement II is true.
3. Statement I is true, but statement II is false.
4. Both statement I and statement II are false.
Answer:
1. Both statement I and statement II are true.

Question 8.
The sequence of chromosome 1 was completed only in
1. April, 2003
2. October, 1990
3. May, 2006
4. December, 2000
Answer:
3. May, 2006

Question 9.
Which of the following is incorrect w.r.t. satellite DNA?
1. These sequences normally do not code for any proteins
2. They form a large portion of human genome.
3. These sequences show high degree of polymorphism.
4. They cannot be used as identification tool in forensic applications.
Answer:
4. They cannot be used as identification tool in forensic applications.

Question 10.
In the technique of DNA fingerprinting, hybridized DNA fragments can be detected by,
1. Gel electrophoresis
2. Restriction endonucleases
3. Western blotting
4. Autoradiography
Answer:
4. Autoradiography

II. Fill in the Blanks

1. In HGP, the DNA fragments were sequenced using automated DNA sequencers that worked on the principle of a method developed by …………………………. .
Answer:
Frederick Sanger

2. Scientists have identified about ………………………. million locations where single base DNA differences occur in humans.
Answer:
1.4

3. Polymorphism (variation at genetic level) arises due to …………………….. .
Answer:
Mutations.

4. In simple terms, if an inheritable mutation is observed in a population at high frequency, it is referred to as ………………….. .
Answer:
DNA polymorphism

5. ………………………… per cent of base sequence among humans is the same.
Answer:
99.9

III. One Word Answer Questions

Question 1.
How many base pairs are present in the human genome?
Answer:
Approximately 3164.7 million base pairs

Question 2.
Who did initially developed the technique of DNA fingerprinting?
Answer:
Alec Jeffreys

Question 3.
Name the class of satellite DNA to which VNTR belongs.
Answer:
Mini-satellite DNA

Question 4.
Which sequences make up a very large portion of the human genome?
Answer:
Repeated DNA sequences

Question 5.
Name the vectors used for cloning DNA fragments during DNA sequencing.
Answer:
BAC (Bacterial Artificial Chromosome) and YAC (Yeast Artificial Chromosome)

Objective Questions

Question 1.
Human Genome Project (HGP) was launched in
1. 1985
2. 1990
3. 1995
4. 2000
Answer:
2. 1990

Question 2.
Human Genome Project is called a
1. Mini project
2. Micro project
3. Mega project
4. Pilot project
Answer:
3. Mega project

Question 3.
The human genome contains approximately
1. 3 × 10⁶ base pairs
2. 3 × 10⁸ base pairs
3. 3 × 10⁹ base pairs
4. 3 × 10¹² base pairs
Answer:
3. 3 × 10⁹ base pairs

Question 4.
One of the main goals of HGP was to identify approximately
1. 2,000 – 5,000 genes
2. 10,000 – 15,000 genes
3. 20,000 – 25,000 genes
4. 50,000 – 60,000 genes
Answer:
3. 20,000 – 25,000 genes

Question 5.
Human Genome Project was completed in
1. 1998
2. 2000
3. 2003
4. 2006
Answer:
3. 2003

Question 6.
HGP was coordinated mainly by
1. WHO
2. U.S. Department of Energy and NIH
3. UNESCO
4. NASA
Answer:
2. U.S. Department of Energy and NIH

Question 7.
Bioinformatics mainly deals with
1. Protein synthesis
2. Data storage, retrieval, and analysis
3. Cell division
4. Photosynthesis
Answer:
2. Data storage, retrieval, and analysis

Question 8.
Expressed Sequence Tags (ESTs) represent
1. Non-coding DNA
2. Genes expressed as RNA
3. Satellite DNA
4. Introns
Answer:
2. Genes expressed as RNA

Question 9.
Sequence annotation refers to
1. DNA digestion
2. Assigning functions to DNA sequences
3. DNA replication
4. RNA translation
Answer:
2. Assigning functions to DNA sequences

Question 10.
DNA fragments during HGP were cloned using
1. Viruses only
2. BAC and YAC vectors
3. Plasmids only
4. Cosmids only
Answer:
2. BAC and YAC vectors

Question 11.
BAC stands for
1. Bacterial Artificial Chromosome
2. Basic Artificial Chromosome
3. Biological Artificial Chromosome
4. Bacterial Active Chromosome
Answer:
1. Bacterial Artificial Chromosome

Question 12.
YAC stands for
1. Yeast Artificial Chromosome
2. Young Artificial Chromosome
3. Yeast Active Chromosome
4. Yellow Artificial Chromosome
Answer:
1. Yeast Artificial Chromosome

Question 13.
Automated DNA sequencing was based on the method developed by
1. Watson
2. Crick
3. Frederick Sanger
4. Mendel
Answer:
3. Frederick Sanger

Question 14.
Alignment of DNA sequences was mainly done using
1. Manual calculation
2. Computer programs
3. Microscope
4. Centrifuge
Answer:
2. Computer programs

Question 15.
The sequence of chromosome 1 was completed in
1. 2003
2. 2004
3. 2005
4. 2006
Answer:
4. 2006

Question 16.
Human genome contains
1. 3164.7 million base pairs
2. 3000 million base pairs
3. 2000 million base pairs
4. 5000 million base pairs
Answer:
1. 3164.7 million base pairs

Question 17.
Average size of a human gene is about
1. 300 bp
2. 3000 bp
3. 30,000 bp
4. 3 lakh bp
Answer:
2. 3000 bp

Question 18.
Largest known human gene is
1. Hemoglobin
2. Insulin
3. Dystrophin
4. Collagen
Answer:
3. Dystrophin

Question 19.
Almost identical nucleotide sequence among humans is
1. 90%
2. 95%
3. 98%
4. 99.9%
Answer:
4. 99.9%

Question 20.
More than …………………………. of discovered genes have unknown functions.
1. 10%
2. 25%
3. 50%
4. 90%
Answer:
3. 50%

Question 21.
Less than …………………………. of human genome codes for proteins.
1. 2%
2. 5%
3. 10%
4. 20%
Answer:
1. 2%

Question 22.
Most of the human genome consists of
1. Protein-coding genes
2. Repeated sequences
3. Ribosomal genes
4. tRNA genes
Answer:
2. Repeated sequences

Question 23.
The chromosome having the maximum number of genes is
1. Chromosome 21
2. Chromosome 1
3. Chromosome X
4. Chromosome Y
Answer:
2. Chromosome 1

Question 24.
The chromosome having the fewest genes is
1. Chromosome 18
2. Chromosome 10
3. Chromosome Y
4. Chromosome X
Answer:
3. Chromosome Y

Question 25.
SNP stands for
1. Single Nucleotide Polymorphism
2. Satellite Nuclear Protein
3. Sequence Number Pattern
4. Single Nuclear Protein
Answer:
1. Single Nucleotide Polymorphism

Question 26.
Scientists identified about ……………………………. million SNP locations in humans.
1. 0.5
2. 1.4
3. 2.5
4. 3.0
Answer:
2. 1.4

Question 27.
DNA fingerprinting mainly compares
1. RNA molecules
2. Protein sequences
3. DNA polymorphism
4. Lipids
Answer:
3. DNA polymorphism

Question 28.
DNA fingerprinting is based on
1. Translation
2. DNA polymorphism
3. Replication
4. Mutation only
Answer:
2. DNA polymorphism

Question 29.
Repetitive DNA is also called
1. Satellite DNA
2. Messenger DNA
3. Coding DNA
4. Template DNA
Answer:
1. Satellite DNA

Question 30.
Satellite DNA is separated by
1. PCR
2. Gel electrophoresis
3. Density gradient centrifugation
4. Chromatography
Answer:
3. Density gradient centrifugation

Question 31.
DNA fingerprinting is highly useful in
1. Blood grouping only
2. Forensic science
3. Plant breeding only
4. Tissue culture
Answer:
2. Forensic science

Question 32.
DNA fingerprinting is widely used in
1. Paternity testing
2. Weather forecasting
3. Blood circulation studies
4. Photosynthesis
Answer:
1. Paternity testing

Question 33.
DNA polymorphism mainly arises due to
1. Nutrition
2. Mutation
3. Pollution
4. Temperature
Answer:
2. Mutation

Question 34.
DNA polymorphism is more common in
1. Coding DNA
2. Non-coding DNA
3. rRNA only
4. tRNA only
Answer:
2. Non-coding DNA

Question 35.
DNA fingerprinting technique was developed by
1. Frederick Sanger
2. Watson
3. Alec Jeffreys
4. Mendel
Answer:
3. Alec Jeffreys

Question 36.
Alec Jeffreys used ……………………… as a probe.
1. mRNA
2. Satellite DNA
3. Plasmid DNA
4. tRNA
Answer:
2. Satellite DNA

Question 37.
VNTR stands for
1. Variable Number of Tandem Repeats
2. Variable Nucleotide Tandem Region
3. Viral Number Tandem Repeat
4. Variable Nuclear Tandem Repeat
Answer:
1. Variable Number of Tandem Repeats

Question 38.
VNTR belongs to
1. Microsatellite
2. Minisatellite
3. Macrosatellite
4. Megasatellite
Answer:
2. Minisatellite

Question 39.
DNA digestion in fingerprinting is carried out by
1. DNA polymerase
2. Restriction endonucleases
3. Ligase
4. Helicase
Answer:
2. Restriction endonucleases

Question 40.
DNA fragments are separated by
1. PCR
2. Electrophoresis
3. Centrifugation
4. Hybridization
Answer:
2. Electrophoresis

Question 41.
Transfer of DNA fragments to a membrane is called
1. Translation
2. Blotting
3. Replication
4. Annealing
Answer:
2. Blotting

Question 42.
Hybridized DNA fragments are detected by
1. Centrifugation
2. Electrophoresis
3. Autoradiography
4. PCR
Answer:
3. Autoradiography

Reviewing AP Inter 2nd Year Zoology Study Material Chapter 3 Principles of Inheritance and Variation Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Zoology 3rd Lesson Principles of Inheritance and Variation Questions and Answers

IV. Very Short Answer Questions

Question 1.
What is Pleiotropy? Give an example.
Answer:

1. Pleiotropy A condition in which a single gene influences more than one phenotypic character.
2. Example: Phenylketonuria (PKU) in humans.

Question 2.
What is polygenic inheritance? Give an example.
Answer:

1. Polygenic inheritance refers to the combined action of two or more genes on a single trait.
2. Example: Human skin colour.

Question 3.
What is aneuploidy?
Answer:
Aneuploidy is a chromosomal condition in which an individual possesses an abnormal chromosome number due to the addition or loss of one or more chromosomes.

Question 4.
What is Klinefelter’s syndrome?
Answer:

1. Klinefelter’s syndrome is a genetic disorder caused by trisomy of the 23rd chromosome pair. The karyotype is 47, XXY. Males possess an additional X chromosome and show the presence of a Barr body.
2. Common features include underdeveloped gonads, decreased fertility, and enlargement of breasts (gynecomastia).

Question 5.
What is Turner’s syndrome?
Answer:

1. Turner’s syndrome is a genetic disorder caused by monosomy of the sex chromosomes; the karyotype is 45, XO, and Barr bodies are absent.
2. Characteristic features include short stature, gonadal dysgenesis, webbed neck, broad chest, and widely spaced nipples.

Question 6.
What is Down’s syndrome?
Answer:

1. Down’s syndrome is a chromosomal disorder characterized by delayed physical growth and intellectual development.
2. It occurs due to the presence of an extra copy of chromosome 21 (Trisomy 21).

Question 7.
Define the terms ‘point mutation’ and ‘frame-shift mutation’.
Answer:

1. Point Mutation: A mutation involving a change in a single nucleotide or base pair of DNA, which may alter the structure or function of a protein.
2. Frameshift Mutation: A mutation caused by the insertion or deletion of one or more nucleotides, resulting in a shift of the reading frame and alteration of the amino acid sequence. ‘

V. Short Answer Questions 

Question 1.
Explain sex determination in human beings.
Answer:
Sex determination in humans:

1. Humans exhibit the XX-XY type of sex determination.
2. Out of the 23 chromosome pairs, 22 pairs are autosomes and 1 pair is made up of sex chromosomes.
3. Females possess the karyotype 44XX, while males possess 44XY.
4. Females produce only one type of gamete carrying the X chromosome, whereas males produce two types of sperms carrying X or Y chromosomes.
5. Female gametes contain 22A+X; male gametes contain either 22A+X or 22A+Y.
6. Fertilization of the ovum by an X-bearing sperm results in a female child (44XX).
7. Fertilization by a Y-bearing sperm produces a male child (44XY).
8. Therefore, the type of sperm that fertilizes the ovum determines the sex of the child.
9. Each pregnancy has an equal 50% chance of producing either a male or female offspring.

Question 2.
Mention any two autosomal Mendelian disorders and write their symptoms.
Answer:
1. Haemophilia:

• Haemophilia is a sex-linked recessive genetic disorder that affects the blood’s ability to clot properly.
• Individuals suffering from this condition experience prolonged and excessive bleeding even from minor cuts or injuries.
• The deficiency of specific clotting factors leads to difficulty in stopping bleeding.
• This disorder is more commonly observed in males, as they have only one X chromosome.

2. Colour Blindness:

• Colour blindness is a sex-linked genetic disorder in which an individual has difficulty distinguishing between certain colours, especially red and green.
• It occurs due to defects in the cone cells of the retina responsible for colour vision.
• This condition does not affect overall vision but impairs the ability to identify colours correctly.
• It is also more frequently found in males than in females.

Question 3.
Describe male heterogamety and female heterogamety method of sex deter¬mination with suitable examples.
Answer:
A. Male Heterogamety: In this system, males produce two types of gametes while females produce only one type. It occurs in two forms:
1. XX-XO Type :

• Found in bugs, grasshoppers, and cockroaches.
• Female genotype: AAXX and produces only AX gametes.
• Male genotype: AAXO and produces AX and AO gametes in equal proportions.
• The sperm determines the sex of the offspring.

2. XX-XY type:

• Found in humans and Drosophila.
• Female genotype: AAXX and produces only AX gametes.
• Male genotype: AAXY and produces AX and AY gametes.
• The sperm carrying X or Y chromosome determines the sex of the offspring.

B. Female Heterogamety: In this type, females produce two kinds of gametes, while males produce only one type. It occurs in two forms:
1. ZO-ZZTvpe:

• Seen in moths and some butterflies.
• Males produce only AZ gametes.
• Female produces AZ and AO ova.
• The ovum determines the sex of the offspring.

2. ZW-ZZ Type:

• Found in certain fishes, reptiles, and birds.
• Female produces AZ and AW ova.
• Male produces only AZ sperms.
• The ovum carrying Z or W chromosome decides the sex of the progeny.

Question 4.
Explain the haplodiploid System of Sex determination in honey bees.
Answer:
The haplodiploid mechanism of sex determination in honey bees depends on the number of chromosome sets present.
1. Females (Queen and Workers):

• Females develop from fertilized eggs formed by the fusion of sperm and ovum.
• They are diploid (2n = 32 chromosomes).

2. Males (Drones) ;

• Males arise from unfertilized eggs through parthenogenesis.
• They are haploid (n = 16 chromosomes).

3. Sperm Formation: Drones produce sperms through mitotic divisions.
4. Family Relationship:

• Drones have no father because they originate from unfertilized eggs.
• However, they possess a grandfather and can have grandsons.

Thus, in honeybees, sex is determined by chromosome number (haploid or diploid) rather than by sex chromosomes.

Question 5.
What is Thalassemia? Explain the two types of Thalassemia in detail.
Answer:

1. Thalassemia is an autosomal recessive blood disorder inherited when both parents carry the defective gene.
2. It results from mutation or deletion of genes responsible for globin chain synthesis.
3. Reduced globin production leads to abnormal haemoglobin formation and causes anaemia.

Types of Thalassemia :
a) Alpha (α) Thalassemia:

• Characterized by reduced synthesis of α-globin chains.
• Controlled by HBA1 and HBA2 genes located on chromosome 16.
• Since four α-globin genes are present (two from each parent), severity depends on the number of affected genes.
• Greater gene deletions result in a more severe condition.

b) Beta (β) Thalassemia :

• Characterized by reduced synthesis of β – globin chains.
• Controlled by the HBB gene located on chromosome 11.
• The disorder develops when one or both β – globin genes are mutated.

VI. Long Answer Questions

Question 1.
Write an essay on common genetic disorders in humans.
Answer:
Common Genetic Disorders: Many human diseases arise due to abnormalities in genes or chromosomes. These disorders are broadly classified into:
I. Mendelian Disorders II. Chromosomal Disorders.
1. Mendelian Disorders: These disorders follow Mendelian inheritance patterns and are usually caused by mutations in a single gene (monogenic disorders). They may be autosomal or sex-linked. Examples: Haemophilia, Sickle-cell anaemia, Phenylketonuria, Colourblindness, Thalassemia, Cystic fibrosis, Albinism, etc.

1. Haemophilia:

• Haemophilia is commonly known as a bleeding disorder because blood fails to clot normally after injury.
• Haemophilia A results from deficiency of clotting factor VIII.
• Haemophilia B results from deficiency of clotting factor IX.
• Both A and B are X-linked recessive disorders.
• Haemophilia C is an autosomal recessive disorder caused by deficiency of clotting factor XI.
• Haemophilia A and B may skip generations.
• The disorder is rare in females because two recessive genes are required.
• It is more frequently observed in males.

2. Sickle-cell Anaemia:

• Sickle-cell anaemia is an autosomal recessive disorder caused by a defective gene located on chromosome 11.
• It is expressed in the homozygous condition.
• Symptoms include weakness, pain, organ damage due to internal bleeding, and sometimes paralysis.
• The disorder results from the substitution of glutamic acid by valine at the sixth position of the beta-globin chain.
• Red blood cells become sickle-shaped and rigid.
• These cells may block capillaries while passing through them.
• Heterozygous individuals may occasionally show mild symptoms but possess increased resistance to malaria.

3. Phenylketonuria (PKU):

• Phenylketonuria was first described by A. Foiling.
• It is an autosomal recessive metabolic disorder.
• The responsible gene is located on chromosome 12.
• Patients lack the enzyme phenylalanine hydroxylase, which converts phenylalanine into tyrosine.
• As a result, phenylalanine is converted into phenylpyruvic acid.
• Accumulation of phenyl ketones may lead to mental retardation.

4. Colour Blindness:

• Colour blindness is an X-linked recessive disorder.
• Protanopia refers to red colour blindness.
• Deuteranopia refers to green colour blindness.
• Affected individuals cannot distinguish red from green colours.
• The Ishihara colour test is commonly used for diagnosis.
• Tritanopia is associated with blue colour blindness and is autosomal in nature.

5. Thalassemia:

• Thalassemia is an autosomal recessive disorder affecting haemoglobin synthesis.
• α-globin genes are located on chromosome 16.
• β – globin genes are located on chromosome 11.
• Defective globin synthesis damages red blood cells.
• RBC count decreases, leading to anaemia.

6. Cystic Fibrosis:

• Cystic fibrosis is an autosomal recessive disorder.
• The defective gene is present on the long arm of chromosome 7.
• It affects the movement of salt and water across cell membranes.

Symptoms:

• Increased sodium and chloride levels in sweat.
• Mucus becomes thick, sticky, and viscous.
• Mucus accumulates in organs such as lungs, pancreas, and intestinal tract.
• Without treatment, patients may die before reaching five years of age.

Question 2.
Write an essay on sex determination;
Answer:
Chromosomal Theory of Sex Determination: In most animals, sex is determined by a pair of chromosomes known as sex chromosomes or allosomes.
The two major sex chromosomes are the X chromosome and Y chromosome.
There are two major systems of chromosomal sex determination:
I. Male Heterogametic Method
II. Female Heterogametic Method
Male Heterogametic Method: In this system, males produce two kinds of gametes, while females produce only one type.

1. XX-XO Type:

• Found in grasshoppers, bugs, and cockroaches.
• Females possess two X chromosomes, whereas males have only one X chromo¬some.’
• The unpaired X chromosome determines maleness.
• Female karyotype is AAXX and male karyotype is AAXO.
• All ova contain the AX complement.
• Sperms are of two types:

1. 50% contain AX
2. 50% contain AO

• The sex of the offspring depends on the sperm that fertilizes the ovum.

2. XX-XY Type:

• Found in humans and Drosophila.
• Females are homogametic with genotype AAXX and produce only AX ova.
• Males are heterogametic with genotype AAXY. homo sapiens
• Half the sperms carry AX, and the other half carry AY.
• The fertilizing sperm determines the sex of the offspring.
• Fertilization by AX sperm produces a female child (AAXX).
• Fertilization by AY sperm produces a male child (AAXY).

II. Female Heterogametic Method: In this type, females produce two kinds of ova, while males produce only one type of sperm. Two forms are recognized:
1. ZO – ZZ Type:

• Found in moths (Fumea) and certain butterflies.
• Females are heterogametic with one Z chromosome.
• Males are homogametic with ZZ chromosomes
• Female karyotype is AAZO and male karyotype is AAZZ.
• The ovum determines the sex of the of Spring.
• Fertilization of an AO ovum produces a female.
• Fertilization of an AZ ovum produces a male.

2. ZW-ZZ Type:

• Found in birds, reptiles, and some fishes.
• Females are heterogametic with ZW chromosomes.
• Males are homogametic with ZZ chromosomes.
• Female karyotype is AAZW and male karyotype is AAZZ.
• The ovum that gets fertilized determines the sex of the offspring.

I. Multiple Choice Questions

Question 1.
Given below are two statements.
Statement I: When many alleles of a single gene govern a character, it is called polygenic inheritance.
Statement II: In polygenic inheritance, the effect of each allele is additive. In the light of the above statements, choose the correct answer from the options given below.
1. Both statement I and statement II are true.
2. Statement I is false, but statement II is true.
3. Statement I is true, but statement II is false.
4. Both statement I and statement II are false.
Answer:
2. Statement I is false, but statement II is true.

Question 2.
The phenomenon of pleiotropy refers to
1. Presence of two alleles, each of the two alleles controlling a single trait.
2. More than two genes affecting a single character.
3. Presence of several alleles of a single gene controlling a single trait.
4. A single gene affecting multiple phenotypic expression.
Answer:
4. A single gene affecting multiple phenotypic expressions.

Question 3.
If a colour blind female marries a man whose mother was also colour blind, what are the chances of her progeny having colour blindness?
1. 25%
2. 50%
3. 75%
4. 100%
Answer:
4. 100%

Question 4.
Which one of the following symbols represents mating between relatives in human pedigree analysis?

2.

3.

4.
Answer:
4.

Question 5.
Which of the following is not an autosome linked recessive trait?
1. Thalassemia
2. Phenylketonuria
3. Haemophilia
4. Sickle-cell anaemia.
Answer:
3. Haemophilia

Question 6.
Inheritance of skin colour in humans is an example of
1. Codominance
2. Multiple allelism
3. Polygenic inheritance
4. Chromosomal aberration.
Answer:
3. Polygenic inheritance

Question 7.
Match List I with List II

Choose the correct answer from the options given below
1. a – ii, b – iii, c – i, d – iv
2. a – ii, b – iii, c – iv, d – i
3. a – iii, b – iv, c – i, d – ii
4. a – iii, b – iv, c – ii, d – i
Answer:
3. a – iii, b – iv, c – i, d – ii

Question 8.
Which of the following statements are correct about Klinefelter’s Syndrome?
i) This disorder was first described by Langdon Down (1866).
ii) Such an individual has overall masculine development; however, the feminine development is also expressed.
iii) The affected individual is short-statured.
iv) Physical, psychomotor, and mental development is retarded.
v) Such individuals are sterile.
1. ii and v only
2. i and iv only
3. i and ii only
4. iii and iv only
Answer:
1. ii and v only

Question 9.
Thalassemia and sickle cell anaemia are caused due to a problem in globin molecule synthesis. Select the correct statement.
1. Both are due to a quantitative defect in globin chain synthesis.
2. Thalassemia is due to less synthesis of globin molecules.
3. Sickle cell anaemia is due to quantitative problem of globin molecules.
4. Both are due to a qualitative defect in globin chain synthesis.
Answer:
2. Thalassemia is due to less synthesis of globin molecules.

Question 10.
Haplodiploid system of sex determination is found in
1. Birds
2. Drosophila
3. Honeybee
4. Grasshoppers
Answer:
2. Drosophila

Question 11.
Assertion: The possibility of a female becoming a haemophilic is extremely rare.
Reason: Mother of such a female has to be at least carrier, and the father should be haemophilic (unviable in the later stage of life). ( 1 )
1. If both Assertion and Reason are true and Reason is the correct explanation of Assertion.
2. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
3. If Assertion is true but Reason is false.
4. If Assertion is false and Reason is true.
Answer:
2. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.

Question 12.
Broad palm with single palm crease is visible in a person suffering from
1. Klinefelter’s syndrome
2. Thalassemia
3. Down’s syndrome
4. Turner’s syndrome
Answer:
3. Down’s syndrome

Question 13.
Which of the following is incorrect with reference to the honey bees?
1. Males do not have father and thus cannot have sons, but have a grandfather and can have grandsons.
2. An unfertilised egg develops as a male bee by means of parthenogenesis.
3. A fertilised egg develops as female bee.
4. Gametes are produced by meiosis in drones.
Answer:
4. Gametes are produced by meiosis in drones.

Question 14.
A disorder caused by an autosomal primary non-disjunction is
1. Klinefelter’s syndrome
2. Turner’s syndrome
3. Sickle cell anaemia
4. Down’s syndrome
Answer:
4. Down’s syndrome

Question 15.
A human female with Turner’s syndrome is characterized by ( 3 )
1. Monosomy of 18
2. Presence of an additional copy of X chromosome, i.e., 47 with XXY
3. Absence of one of the X chromosomes, i.e., 45 with XO
4. Trisomy of 18
Answer:
3. Absence of one of the X chromosomes, i.e., 45 with XO

II. Fill in the Blanks

1. A person who is suffering from phenylketonuria lacks an enzyme that converts the amino acid phenylalanine into ……………………… .
Answer:
Tyrosine

2. In addition to recombination, ……………………………… is another phenomenon that leads to variation in DNA.
Answer:
Mutation.

3. Sickle-cell anaemia is caused by the substitution of glutamic acid (Glu) ……………………… at the sixth position of the beta globin chain of the haemoglobin molecule.
Answer:
Valine (VAL)

4. Henking gave a name to a specific nuclear structure that present in 50 per cent of sperms in few insects as the ………………………. .
Answer:
X body.

5. Failure of segregation of chromosomes during cell division cycle results in the gain or loss of a chromosome(s) called ……………………….. .
Answer:
Aneuploidy.

III. One Word Answer Questions

Question 1.
Which type of sex determination is found in Grasshoppers?
Answer:
XO Type

Question 2.
Which Mendelian disorder is controlled by two closely linked genes HBA1 and HBA2 on chromosome 16?
Answer:
α -Thalassemia

Question 3.
Which syndrome is characterized by presence of rudimentary ovaries and lack of other secondary sexual characters?
Answer:
Turner’s syndrome

Question 4.
Accumulation of which substances in brain results in mental retardation in an individual suffering from PKU?
Answer:
Phenylpyruvic acid and other derivatives of phenylalanine.

Question 5.
Name the type of mutations which are caused due to deletions and insertions of base pairs of DNA.
Answer:
Frame-shift mutations

Objective Questions

Question 1.
When genes are arranged on a chromosome, the arrangement is known as:
1. Spiral
2. Ovoid
3. Linear
4. Radial
Answer:
3. Linear

Question 2.
The blood group B possesses:
1. B antigen in plasma
2. B antigens on RBCs
3. B antibodies in plasma
4. A antigen on RBC
Answer:
2. B antigens on RBCs

Question 3.
Another term used for codominance is:
1. Equal dominance
2. Mutual dominance
3. Paternal character
4. Maternal dominance
Answer:
1. Equal dominance

Question 4.
Down syndrome results from:
1. Tetrasomy of 22nd chromosome
2. Trisomy of 21st chromosome
3. Monosomy of 21st chromosome
4. Polysomy of 9th chromosome
Answer:
2. Trisomy of 21st chromosome

Question 5.
Factors responsible for heredity are known as:
1. Tissues
2. Cells
3. Genes
4. Zygotes
Answer:
3. Genes

Question 6.
Satellite DNA is widely used in :
1. Genetic engineering
2. Forensic science
3. Sex determination
4. Organ transplantation
Answer:
2. Forensic science

Question 7.
The branch of biology that studies heredity:
1. Ethology
2. Physiology
3. Genetics
4. Psychology
Answer:
3. Genetics

Question 8.
Which of the following fields does NOT belong to genetics?
1. Study of heredity
2. Study of evolution
3. Study o f variation
4. Study of transmission of characters
Answer:
2. Study of evolution

Question 9.
When a single gene influences multiple traits, the phenomenon is called:
1. Incomplete dominance
2. Pleiotropy
3. Epistasis
4. Codominance
Answer:
3. Epistasis

Question 10.
Identify the genetic disorder among the following:
1. Cholera
2. Sickle cell anaemia
3. Diabetes
4. Typhoid
Answer:
3. Diabetes

Question 11.
The blood group lacking antigens on RBC surface is:
1. B group
2. AB group
3. A group
4. O group
Answer:
4. O group

Question 12.
AB antigens are chemically:
1. Glycoproteins
2. Lipids
3. Proteins
4. Sugar polymers
Answer:
4. Sugar polymers

Question 13.
In O blood group, RBCs possess:
1. A antigen
2. B antigen
3. No antigens
4. A, B antigens
Answer:
3. No antigens

Question 14.
Anti-A and Anti-B antibodies belong to:
1. Ig E type
2. Ig G type
3. Ig M type
4. Ig I type
Answer:
3. Ig M type

Question 15.
The genotype I^AI^B corresponds to:
1. B group
2. AB group
3. O group
4. A group
Answer:
2. AB group

Question 16.
Genes controlling Rh factor are located on:
1. 12th chromosome
2. 1st chromosome
3. 21st chromosome
4. 9th chromosome
Answer:
2. 1st chromosome

Question 17.
In codominance, the phenotype displays:
1. Maternal character
2. Both paternal and maternal characters equally
3. Neither (1) nor (2)
4. Paternal character
Answer:
2. Both paternal and maternal characters equally

Question 18.
If the genotypic ratio is 1:2:1 under codominance. the phenotypic ratio be conies:
1. 3:1
2. 3
3. 1: 2: 1
4. 1:3
Answer:
3. 1: 2: 1

Question 19.
Human skin colour demonstrates:
1. Multiple allelism
2. Polygenic inheritance
3. Multiple phenotypes
4. Pleiotropy
Answer:
2. Polygenic inheritance

Question 20.
Genes responsible for skin colour but lacking pigment production are termed:
1. Neutral genes
2. Non-pigment genes
3. Submissive genes
4. Pleiotropic genes
Answer:
1. Neutral genes

Question 21.
Chromosomes involved in sex determination are called:
1. Polysomes
2. Allosomes
3. Autosomes
4. Pleasomes
Answer:
2. Allosomes

Question 22.
Human beings exhibit which sex-determination pattern?
1. ZZ – ZO type
2. XX – YY type
3. ZW – ZZ type
4. XX – XO type
Answer:
2. XX – YY type

Question 23.
How many X chromosomes are present in a normal human female?
1. Eight
2. Four
3. Two
4. Six
Answer:
3. Two

Question 24.
The X: A ratio in a normal female Drosophila is :
1. 0.5
2. 1.0
3. 1.5
4. 0.67
Answer:
3. 1.5

Question 25.
Sex-linked genes are found on :
1. Y-chromosome
2. Autosomes
3. X or Y chromosome
4. X-chromosome
Answer:
1. Y-chromosome

Question 26.
Colour blindness, haemophilia and Duchenne muscular dystrophy show:
1. X- linked dominant inheritance
2. X- linked recessive inheritance
3. Y-linked inheritance
4. XY-linked dominant inheritance
Answer:
2. X-linked recessive inheritance

Question 27.
The largest identified human gene is:
1. Melanin gene
2. Dystrophin gene
3. Insulin gene
4. Chromatin gene
Answer:
2. Dystrophin gene

Question 28.
Diseases produced due to mutations in a single gene are known as :
1. Nutritional disorders
2. Chromosomal diseases
3. Mendelian disorders
4. Hormonal diseases
Answer:
3. Mendelian disorders

Question 29.
Haemophilia ‘A’ occurs due to deficiency of:
1. Clotting factor XI
2. Clotting factor IX
3. Clotting factor VIII
4. Clotting factor X
Answer:
3. Clotting factor VIII

Question 30.
PKU results from deficiency of:
1. Phenylalanine carboxylase
2. Phenylalanine hydroxylase
3. Phenylalanine dehydrogenase
4. Phenylalanine hydroxylase
Answer:
2. Phenylalanine hydroxylase

Question 31.
The approximate number of chemical base pairs in human DNA is:
1. 8 billion
2. 3 2 billion
3. 2.2 billion
4. 3.8 billion
Answer:
2. 3 2 billion

Question 32.
In the Human Genome Project, cloning leads to :
1. Fragmentation of DNA
2. Amplification of DNA
3. Segregation of DNA
4. Mutation of DNA
Answer:
2. Amplification of DNA

Question 33.
DNA sequencing technique was developed by:
1. Frederick Sanor
2. Frederick Sanger
3. National Institute of Health
4. Ion wilmot
Answer:
2. Frederick Sanger

Question 34.
The number of genes present on chromosome 1 is :
1. 8296
2. 2968
3. 6928
4. 9268
Answer:
2. 2968

Question 35.
The genotype responsible for intersex Drosophila is :
1. 2A+XXX
2. 2A+XXY
3. 3A+XXY
4. 2A+XY
Answer:
3. 3A+XXY

Question 36.
The chromosome constitution of a male grasshopper is :
1. 2A+YY
2. 2A+XO
3. 2A+XY
4. 2A+XX
Answer:
2. 2A+XO

Question 37.
Sickle-cell anaemia is caused due to :
1. Change of Amino Acid in either α or β chain of Haemoglobin
2. Change of Amino Acid in β-chain of Haemoglobin
3. Change of Amino Acid in α-chain of Haemoglobin
4. Change of Amino Acid in both α and β chain of Haemoglobin
Answer:
2. Change of Amino Acid in β-chain of Haemoglobin

Question 38.
Drosophila melanogaster possesses :
1. 3 pairs of autosomes and 3 pairs of sex chromosomes
2. 3 pairs of autosomes and 1 pair of sex chromosomes
3. 2 pairs of autosomes and 1 pair of sex chromosomes
4. 1 pair of autosomes and 3 pairs of sex chromosomes
Answer:
2. 3 pairs of autosomes and 1 pair of sex chromosomes

Question 39.
Barr body is associated with :
1. Autosome of female
2. Sex chromosome of female
3. Sex chromosome of male
4. Autosome of male
Answer:
2. Sex chromosome of female

Question 40.
Human skin colour inheritance is an example of:
1. Pleiotropy
2. Sex-linked inheritance
3. Polygenic inheritance
4. Multiple allelism
Answer:
3. Polygenic inheritance

Question 41.
The XX-XO type of male heterogamety occurs in :
1. Moths
2. Grasshoppers
3. Drosophila
4. Butterflies
Answer:
2. Grasshoppers

Question 42.
Minisatellites or VNTRs are mainly utilized in :
1. Polymerase Chain Reaction (PCR)
2. Gene mapping
3. DNA fingerprinting
4. Gene therapy
Answer:
3. DNA fingerprinting

Question 43.
In Alpha Thalassemia, the HBA1 gene is located on chromosome :
1. 8
2. 16
3. 9
4. 22
Answer:
2. 16

Question 44.
A woman with blood group O has two brothers, one with blood group A and another with blood group B. The possible genotypes of her parents are :
1. I^AI^B – I°I°
2. I^AI° – I^AI°
3. I°I° – I^AI°
4. I^AI° – I^BI°
Answer:
4. I^AI° – I^BI°

Question 45.
Identify the true statements regarding Klinefelter syndrome.
A) Feminine sexual development is not completely suppressed
B) Karyotype is 44, XXY
C) Male negative for Barr body
D) Secondary sexual characters are well developed
1. A & B
2. B & C
3. C & D
4. B & D
Answer:
1. A & B

Question 46.
In a heterozygous individual, equal expression of both alleles in the phenotype is known as:
1. Rh factor
2. Colour blindness
3. A & B blood types
4. AB blood type
Answer:
4. AB blood type

Question 47.
In colour blindness inheritance, the trait from a colour-blind man is transmitted to :
1. Son
2. Grandson
3. Granddaughter
4. Daughter
Answer:
4. Daughter

Question 48.
A normal woman whose father is colour blind marries a normal man. Their sons will be :
1. All colour blind
2. 50% colour blind
3. 75% colour blind
4. All normal
Answer:
2. 50% colour blind

Question 49.
Inheritance involving many genes in humans is seen in :
1. Sickle cell anaemia
2. Phenylketonuria
3. Skin colour
4. Colour blindness
Answer:
3. Skin colour

Question 50.
Barr body is present in :
1. Ovum
2. Somatic cell of male
3. Somatic cell of female
4. Sperm
Answer:
3. Somatic cell of female

Question 51.
“Cri-du-Chat” syndrome results from a chromosomal structural change
1. Translocation
2. Males produce two types of gametes while females produce one type of gamete
3. Females produce two types of gametes
4. Males as well as females produce two types of gametes
Answer:
3. Females produce two types of gametes

Question 52.
The sex determination mechanism found in poultry birds is:
1. Hormonalmethod
2. XX – XY method
3. ZW – ZZ method
4. XO method
Answer:
3. ZW – ZZ method

Question 53.
In Drosophila, factors essential for male fertility are located on :
1. X chromosome, Autosomes
2. Autosomes
3. X chromosome
4. Y chromosome
Answer:
4. Y chromosome

Question 54.
In the ZW-ZZ pattern of sex determination:
1. Males produce two types of gametes
2. Males produce two types of gametes while females produce one type of gamete
3. Females produce two types of gametes
4. Male as well as female produce two types of gametes
Answer:
3. Females produce two types of gametes

Question 55.
Drumstick body occurs in certain :
1. Fibroblasts of females
2. Fibroblasts of males
3. Neutrophils of females
4. Neutrophils of males
Answer:
3. Neutrophils of females

Question 56.
In honey bees, equal chromosome numbers are found in :
1. Unfertilized egg and queen
2. Drone and ovum
3. Drone and worker
4. Queen and drone
Answer:
2. Drone and ovum

Question 57.
Y-linked genes:
1. Exist in the homozygous state in males
2. Exist in the hemizygous state in females
3. Exist in the hemizygous state in males
4. Exist in the homozygous state in females
Answer:
3. Exist in the hemizygous state in males

Question 58.
A trait that is not associated with Y-linked inheritance :
1. Genes are always hemizygous
2. Webbing of toes is found only in males
3. Genes pass from father to son
4. Genes are dominant or recessive in expression
Answer:
4. Genes are dominant or recessive in expression

Question 59.
If the father is non-bald and the mother is bald, the probability of sons becoming bald is :
1. 0%
2. 50%
3. 25%
4. 100%
Answer:
4. 100%

Question 60.
If a human male somatic cell contains a single Barr body, the genotype is:
1. XO
2. XXY
3. XXXY
4. XYY
Answer:
2. XXY

Question 61.
If mother has blood group B and father has blood group A, the offspring may be:
1. O group
2. A group
3. AB
4. Any of the above
Answer:
4. Any of the above

Question 62.
Polydactyly in humans is due to:
1. Sex-linked recessive gene
2. Autosomal recessive gene
3. Autosomal dominant gene
4. Sex-linked dominant gene
Answer:
3. Autosomal dominant gene

Question 63.
Which symbol and its meaning are correctly matched in human pedigree analysis?
1. O = unaffected male
2. ♦ = male affected
= meeting between relatives
4. □ = unaffected female
Answer:
= meeting between relatives

Reviewing AP Inter 2nd Year Zoology Study Material Chapter 2 Reproductive Health Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Zoology 2nd Lesson Reproductive Health Questions and Answers

IV. Very Short Answer Questions

Question 1.
What in your view, are the reasons for population explosion, especially in India?
Answer:

1. Significant reduction in the death rate.
2. Decrease in Maternal Mortality Rate (MMR).
3. Reduction in Infant Mortality Rate (IMR).
4. Increase in the number of people belonging to the reproductive age group.

Question 2.
What is amniocentesis? Name any two disorders that can be detected through amniocentesis.
Answer:
1. Amniocentesis is a prenatal diagnostic technique used to identify genetic abnormalities in an unborn child.
2. Disorders that can be detected include:

• Down syndrome
• Edward’s syndrome
• Tumer’s syndrome

3. In this procedure, a sample of amniotic fluid is collected, and foetal cells are examined.
4. However, misuse of this method for determining the sex of the foetus has led to legal restrictions.

Question 3.
List out the contraceptive methods available to the couples.
Answer:

1. Periodic abstinence
2. Condoms
3. Vasectomy (male sterilization)
4. Tubectomy (female sterilization)
5. Coitus interruptus (withdrawal method)

Question 4.
Mention the advantage of Lactational Amenorrhea. (APMAY-22)(APMAR.-19,24)
Answer:
Advantages of Lactational Amenorrhea (Breastfeeding Method):

1. During the period of exclusive breastfeeding, the likelihood of conception is extremely low.
2. Breastfed infants receive enhanced immunity and protection against allergic conditions.

Question 5.
List the different types of Intrauterine Devices (IUDs) used to avoid pregnancy.
Answer:
The various categories of Intrauterine Devices (IUDs) are:

1. Non-medicated IUDs Example: Lippes Loop
2. Copper-releasing IUDs Examples: Cu-T (Copper-T), Cu-7, Multiload 375
3. Hormone-releasing IUDs Examples: Progestasert, LNG-20

Question 6.
Mention the mode of action of oral contraceptive pills (daily pills) in preventing pregnancy.
Answer:

1. Oral contraceptive pills mainly prevent pregnancy by suppressing ovulation.
2. They also increase the thickness of cervical mucus, thereby restricting sperm entry into the uterus, and alter the endometrium, making it unfavorable for implantation.

Question 7.
What measures should one take to prevent sexually transmitted diseases (STDs)? (AP MAR-17, 23)
Answer:
Measures to Prevent STDs:

1. Avoid sexual contact with unknown individuals or multiple partners.
2. Use condoms consistently during sexual intercourse.
3. Seek medical consultation for early diagnosis of STDs.
4. Complete the prescribed treatment if an infection is detected.

8. What are the reasons for infertility in human beings?
Answer:

1. Infertility may result from physical abnormalities, hormonal imbalances, infections or diseases i (including STIs), and genetic disorders.
2. It may also arise due to a low sperm count or other male reproductive problems.

V. Short Answer Questions 

Question 1.
Why is the introduction of sex education in schools is necessary?
Answer:

1. Sex education is important because adolescents experience many physical and emotional changes and are naturally curious about reproductive processes.
2. Accurate knowledge about reproductive organs, adolescence, bodily changes, and safe hygienic practices helps students understand these developments properly.
3. Awareness about sexually transmitted diseases enables students to recognize the consequences of unsafe sexual behavior.
4. Therefore, school students should receive scientifically correct information regarding sex and reproductive health.

Question 2.
Describe the following contraceptive methods.
(a) Natural Methods
(b) Surgical Methods
Answer:
(a) Natural Methods of Contraception: Natural methods prevent pregnancy by avoiding the meeting of sperm and ovum.

1. Periodic Abstinence: The couple refrains from sexual intercourse during the fertile period (usually from the 10th to 17th day of the menstrual cycle), thereby reducing the chances of fertilization.
2. Withdrawal or Coitus Interruptus: The male partner withdraws the penis before ejaculation, preventing sperm from entering the female reproductive tract.

(b) Surgical Methods of Contraception: These methods are permanent sterilization procedures.

1. Vasectomy: A small incision is made on both sides of the scrotum, and a portion of the vas deferens is cut and tied. This prevents sperm from reaching the seminal fluid, making the semen free of sperms.
2. Tubectomy: Small incisions are made on both sides of the lower abdomen. A section of each fallopian tube is cut and tied, preventing the ovum from reaching the site of fertilization and thereby preventing pregnancy.

Question 3.
Which barrier methods are effectively useful for newly married couples to avoid conception?
Answer:
Barrier methods prevent fertilization by physically blocking the meeting of sperm and ovum.

1. Condoms (Male and Female): These are thin latex or rubber coverings used over the penis or inside the female reproductive tract. They are easily available, disposable, provide privacy, and also offer protection against STIs and AIDS.
2. Diaphragms, Cervical Caps, and Vaults: These devices are inserted into the female reproductive tract to cover the cervix and prevent sperm entry. They can be reused and are effective contraceptive barriers.
3. Spermicidal Agents: Creams, jellies, and foams are used along with barrier devices to destroy or immobilize sperms, thereby increasing contraceptive effectiveness. These methods are safe, reversible, user-friendly, and have very few side effects, making them suitable for newly married couples.

Question 4.
Write short notes on any two of the following.
(a) MTP (Medical Termination of Pregnancy)
(b) RTI (Reproductive Tract Infections)
(c) SAHELI
Answer:
(a) MTP (Medical Termination of Pregnancy): MTP refers to the deliberate termination of pregnancy before full-term development using medical or surgical procedures.

• It is performed in cases of unwanted pregnancy, contraceptive failure, or when pregnancy poses a risk to the mother’s health.
• It is considered safer when carried out during the early stages of pregnancy.
• Proper medical supervision is essential to avoid complications.

RTIs are infections affecting the reproductive organs and may be caused by bacteria, viruses, or other microorganisms.

• They may spread through sexual contact (STIs) or result from poor hygiene.
• Common symptoms include pain, abnormal discharge, itching, and infertility if untreated.
• Early diagnosis and proper treatment help prevent complications.

SAHELT is an oral contraceptive pill developed in India.

• It is a non-steroidal, once-a-week pill that is convenient to use.
• It produces fewer side effects when compared to many hormonal contraceptive pills.
• It is widely used as a method of family planning and birth control.

Question 5.
Write short notes on any two of the following, suggesting some methods that can help infertile couples to have children.
(a) IVF (In Vitro Fertilization)
(b) GIFT (Gamete Intra Fallopian Transfer)
(c) ICSI (Intra-Cytoplasmic Sperm Injection)
Answer:
(a) IVF-In Vitro Fertilization :

• Fertilization of the ovum takes place outside the body under laboratory conditions.
• The developing embryo is cultured up to the early stage and then transferred into the uterus.
• This technique is commonly known as the test-tube baby technique.
• The sperm and ovum may be obtained either from the couple themselves or from donors.
• The embryo may be implanted in the biological mother or a surrogate mother.

(b) GIFT (Gamete Intra Fallopian Transfer):

• GIFT is an Assisted Reproductive Technology (ART) used to help infertile couples achieve pregnancy.
• In this method, an ovum (egg) collected from a donor is transferred into the fallopian tube of another female. Fertilization occurs naturally inside the body (in vivo).
• It is useful for women who cannot produce ova but possess normal fallopian tubes and a healthy uterus capable of supporting embryo development.

(c) ICSI (Intra-Cytoplasmic Sperm Injection):

• ICSI is a specialized ART technique in which a single sperm is directly injected into the ovum to facilitate fertilization.
• This method is especially useful in cases of very low sperm count or poor sperm quality.
• The resulting embryo is later transferred into the uterus for further development.

I. Multiple Choice Questions

Question 1.
Amniocentesis is used to detect genetic diseases like.
1) Hepatitis B
2) HIV
3) Haemophilia
4) Syphilis
Answer:
3) Haemophilia

Question 2.
Identify the Intrauterine device (IUD).
1) Diaphragms
2) Lippes Loop
3) Cervical Caps
4) Condom
Answer:
2) Lippes Loop

Question 3.
The sterilization procedure in the male is called.
1) Vasectomy
2) Tubectomy
3) Periodic Abstinence
4) MTP
Answer:
1) Vasectomy

Question 4.
The Transfer of the Zygote or early embryo (with upto 8 blastomeres) into the Fallopian Tube is called.
1. GIFT
2) ICSI
3) ZIFT
4) IUI
Answer:
3) ZIFT

Question 5.
In vitro fertilization (IVF), followed by the transfer of embryo into the female genital tract, is called.
1. IUI
2) Test Tube baby
3) GIFT
4) IVI
Answer:
3) GIFT

Question 6.
What are the major tasks of “Reproductive and Child Health Care (RCH) programmes”?
a) Creating awareness among people about various reproduction-related aspects,
b) Providing facilities regarding reproductive and child health care;
c) Support for building up a reproductively healthy society,
d) Encouraging population explosion
1. a,b only
2) c,d only
3) a,b,c only
4) a,c,d only
Answer:
3) a,b,c only

Question 7.
Which of the following statements is correct?
1. Abortions could happen spontaneously too.
2. Infertility is defined as the inability to produce a viable offspring and is always due to Abnormalities/ defects in the female partner.
3. Completely lactation could help as a barrier method of Contraception.
4. Tubectomy prevents transportation of gametes in males.
Answer:
3. Completely lactation could help as a barrier method of Contraception.

II. Fill in the Blanks

1. Genetic disorders like Down syndrome, Haemophilia, sickle cell anaemia are detected by method.
Answer:
Amniocentesis

2. Central Drug Research Institute (CDRI) is located in ……………………….. .
Answer:
Lucknow

3. The Terminal surgical method to pregnancy is called ……………………… .
Answer:
Sterilization

4. In India, the medical termination of pregnancy (MTP) is legalized in the year ……………………… .
Answer:
1971

5. In …………………….. technique, semen collected from the husband or healthy donor is artificially introduced into the vagina or into the uterus.
Answer:
Intrauterine insemination

III. One Word Answer Questions

Question 1.
Name the new oral contraceptive pill for the females developed by Central Drug Research Institute.
Answer:
SAHELI

Question 2.
Which age group of persons are more vulnerable to the reproductive tract infections and venereal diseases (VDs)?
Answer:
15 to 24 Years.

Question 3.
What are the commonly known special techniques used to help infertile couples to have children?
Answer:
Assisted Reproductive Technologies (ART).

Question 4.
Name the method in which a sperm is directly injected into the ovum.
Answer:
Intra Cytoplasmic Sperm injection.

Question 5.
In which year was a “family planning” program initiated in India?
Answer:
1951.

Objective Questions

Question 1.
Which of the following is an example of an IUD?
1. Copper-T
2. Condom
3. Vasectomy
4. Pill
Answer:
1. Copper-T

Question 2.
Which substances are present in contraceptive pills?
1. Progesterone and estrogen
2. Spermicidal salts
3. Chemicals causing automatic abortion
4. Chemicals that prevent fertilization of ovum
Answer:
1. Progesterone and estrogen

Question 3.
What does the abbreviation MTP stand for?
1. Multi trade practices
2. Malthusian theory on populations
3. Multiple temporary frequency
4. Medical termination of pregnancy
Answer:
4. Medical termination of pregnancy

Question 4.
Tubectomy is mainly performed to prevent
1. Coitus
2. Eggs formation
3. Fertilization
4. Embryonic development
Answer:
3. Fertilization

Question 5.
Which hormone is an important component of oral contraceptive pills?
1. Thyroxine
2. LH
3. Progesterone
4. GH
Answer:
3. Progesterone

Question 6.
Tubectomy, as a method of population control, is carried out on
1. Both males and females
2. Males only
3. Females only
4. Only pregnant women
Answer:
3. Females only

Question 7.
Which of the following is a commonly adopted method of sterilization?
1. IUCD
2. Diaphragm
3. Tubectomy
4. Loop
Answer:
3. Tubectomy

Question 8.
Which mechanical barrier is commonly used for birth control?
1. Copper-T
2. Diaphragm
3. Loop
4. Dalcon shield
Answer:
2. Diaphragm

Question 9.
Which statement correctly describes surrogacy?
1. Surrogate mother is biological mother for the baby
2. The baby will have two biological fathers
3. A woman provides her uterus for the development of someone else’s embryo
4. None
Answer:
3. A woman provides her uterus for the development of some other’s embryo

Question 10.
Which statement about a test tube baby is correct?
1. Fertilization inside female genital tract and growth in test tube
2. Rearing of prematurely bom baby in incubator
3. Fertilization outside and gestation inside the womb of mother
4. Both fertilization and development outside the female genital tract
Answer:
3. Fertilization outside and gestation inside the womb of mother

Question 11.
W hy is breastfeeding considered the best feeding?
1. enhances immunity
2. protects against allergies
3. reduces chances of immediate conception
4. all the above
Answer:
4. all the above

Question 12.
Assisted Reproductive Technology (ART), in which the ‘Test Tube Baby’ technique is employed, is known as
1. Gamete intrafallopian transfer (GIFT)
2. Intracytoplasmic sperm injection (ICSI)
3. In vitro fertilization and embryo transfer (IVF/ET)
4. Zygote intrafallopian transfer (ZIFT)
Answer:
3. In vitro fertilization and embryo transfer (IVF/ET)

Question 13.
Which of the following is a major constituent of oral contraceptive pills?
1. progesterone
2. oxytocin
3. relaxin
4. oiplex
Answer:
1. progesterone

Question 14.
Oral contraceptive pills help in preventing pregnancy by
1. killing the sperms in uterus
2. preventing implantation
3. preventing ovulation
4. both (2) and (3)
Answer:
4. both (2) and (3)

Question 15.
Amniocentesis is carried out for
1. digestion of amino acids
2. conversion of glucose to amino acids
3. taking out of cells near the foetus
4. killing of child before birth
Answer:
3. taking out of cells near the foetus

Question 16.
The Gamete Intra Fallopian Transfer (GIFT) technique is recommended for women
1. who cannot produce an ovum
2. who cannot retain the foetus inside uterus
3. whose cervical canal is too narrow to allow passage for the sperms
4. who cannot provide suitable environment for fertilization
Answer:
1. who cannot produce an ovum

Question 17.
Which of the following is a legally accepted method of birth control?
1. by abstaining from coitus from day 10 to 17 of the menstrual cycle
2. by having coitus at the time of day break
3. by a premature ejaculation during coitus
4. abortion by taking an appropriate medicine
Answer:
4. abortion by taking an appropriate medicine

Question 18.
Which of the following acts as a hormone-releasing Intrauterine Device (IUD)?
1. Multiload 375
2. LNG – 20
3. Cervical cap
4. Vault
Answer:
2. LNG – 20

Question 19.
Identify the incorrectly matched pair.
1. syphilis – Trichuris trichiura
2. sleeping sickness – Trypanosoma gambiense
3. dengue Fever – arbovirus
4. plague – Yersinia pestis
Answer:
1. syphilis – Trichuris trichiura

Question 20.
Progesterone pill helps to avoid pregnancy mainly by preventing
1. ovum formation
2. fertilization
3. implantation
4. none of these
Answer:
1. ovum formation

Question 21.
GIFT involves the transfer of
1. a mixture of sperms and ova into the uterus
2. embryo into the uterus
3. a mixture of sperms and ova into the Fallopian tube
4. zygote into the Fallopian tube
Answer:
3. a mixture of sperms and ova into the Fallopian tube

Question 22.
In vitro fertilisation is a technique that involves transfer of which of the following into the Fallopian tube? ( 2 )
1. Embryo only, up to 8-cell stage
2. Either zygote or early embryo up to 8-cell stage
3. Embryo of 32-cell stage
4. Zygote only
Answer:
2. Either zygote or early embryo up to 8-cell stage

Question 23.
Amniocentesis is mainly permitted for
1. detecting sex of the unborn foetus
2. artificial insemination
3. transfer of embryo into the uterus of a surrogate mother
4. detecting any genetic abnormality
Answer:
4. Detecting any genetic abnormality

Question 24.
Up to how many weeks is Medical Termination of Pregnancy (MTP) considered safe?
1. Eight weeks
2. Twelve weeks
3. Eighteen weeks
4. Six weeks
Answer:
2. Twelve weeks

Question 25.
Which of the following cannot be identified in a developing foetus through amniocentesis?
1. Down’s syndrome
2. Jaundice
3. Klinefelter’s syndrome
4. Sex of the foetus
Answer:
2. Jaundice

Question 26.
Tubectomy is a sterilization method in which
1. small part of the Fallopian tube is removed or tied up
2. ovaries are removed surgically
3. small part of vas deferens is removed or tied up
4. uterus is removed surgically
Answer:
1. small part of the Fallopian tube is removed or tied up

Question 27.
Copper-releasing intrauterine devices (IUDs) release Cu ions to
1. make uterus unsuitable for implantation
2. increase phagocytosis of sperms
3. suppress sperm motility
4. prevent ovulation
Answer:
3. suppress sperm motility

Question 28.
In assisted reproductive technology, IVF involves the transfer of
1. ovum into the Fallopian tube
2. zygote into the Fallopian tube
3. zygote into the uterus
4. embryo with 16 blastomeres into the Fallopian tube
Answer:
2. Zygote into the Fallopian tube

Question 29.
Which of the following is not a sexually transmitted disease?
1. Trichomoniasis
2. Encephalitis
3. Syphilis
4. Acquired Immunodeficiency Syndrome (AIDS)
Answer:
2. Encephalitis

Question 30.
Which virus is not transmitted through the semen of an infected male? ( 1 )
1. Chikungunya virus
2. Ebola virus
3. Hepatitis B virus
4. Human immunodeficiency virus
Answer:
1. Chikungunya virus

Question 31.
A childless couple can be helped through a technique called GIFT. What is the full form of GIFT?
1. Gamete Internal Fertilisation and Transfer
2. Germ cell Internal Fallopian Transfer
3. Gamete Inseminated Fallopian Transfer
4. Gamete Intra Fallopian Transfer
Answer:
4. Gamete Intra Fallopian Transfer

Question 32.
In embryo transfer, embryos produced by in vitro fertilisation are transferred into the
1. uterus
2. Fallopian tube
3. fimbriae
4. cervix
Answer:
1. uterus

Question 33.
Genital warts are caused by
1. Herpes simplex virus (HSV)
2. Treponema pallidum
3. Trichomonas vaginalis
4. Human papillomavirus (HPV)
Answer:
4. Human papillomavirus (HPV)

Question 34.
Which of the following techniques involves the direct introduction of gametes into the oviduct?
1. MTPS
2. ET
3. IVF
4. GIFT
Answer:
4. GIFT

Question 35.
Which of the following is a method of birth control?
1. IUDS
2. GIFT
3. HTF
4. IVF-ET
Answer:
1. IUDS

Question 36.
Syphilis is caused by
1. Treponema pallidum
2. Plasmodium
3. Neisseria gonorrhea
4. Entamoeba histolytica
Answer:
1. Treponema pallidum

Reviewing AP Inter 2nd Year Zoology Study Material Chapter 1 Human Reproduction Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Zoology 1st Lesson Human Reproduction Questions and Answers

IV. Very Short Answer Questions

Question 1.
What are the functions of Sertoli cells of the seminiferous tubules and the Leydig cells in man? (AP MAY-22)
Answer:
Sertoli cells :

1. Sertoli cells act as supporting and nourishing cells for developing sperm cells.
2. They also secrete Inhibin, a hormone that helps regulate FSH secretion.
3. These cells are present within the seminiferous tubules along with germ cells.

Leydig Cells

1. Leydig cells are found in the spaces between seminiferous tubules.
2. They produce and release androgens, particularly testosterone, which is essential for male reproductive functions.

Question 2.
Define spermiogenesis and spermiation. (AP MAR-25)
Answer:

1. Spermiogenesis: The process through which spermatids differentiate and mature into spermatozoa (sperms).
2. Spermiation: The process in which mature spermatozoa are released from the seminiferous tubules into their lumen.

Question 3.
Draw a labelled diagram of a sperm.
Answer:

Question 4.
What are the major components of seminal plasma?
Answer:
The important constituents of seminal plasma include:

1. Fructose
2. Calcium
3. Mucus
4. Ascorbic Acid (Vitamin C)

Question 5.
What is the menstrual cycle? Which hormones regulate menstrual cycle?
Answer:
1. The menstrual cycle is the regular reproductive cycle seen in human female primates.
2. During each cycle, the endometrium undergoes preparation for pregnancy and is shed if fertilization does not occur.
3. In human females, these cyclic changes generally occur every28-29 days.
4. The cycle is mainly controlled by the following hormones:

• Follicle-stimulating hormone (FSH) – Pituitary gland
• Luteinizing Hormone (LH) – Pituitary gland
• Estrogen – Ovary
• Progesterone – Ovary.

Question 6.
What is parturition? Which hormone are involved in inducing parturition?
Answer:

1. Parturition is the process of childbirth or the delivery of a baby from the uterus.
2. Oxytocin plays a major role in initiating and facilitating parturition.

Question 7.
How many eggs are released by a human ovary in a month? How many eggs do you think would have been released if the mother gave birth to identical twins? Would your answer change if the twins were fraternal?
Answer:

1. Normally, one ovum is released from a human ovary during each menstrual cycle.
2. In the case of identical twins, only one egg is released and later divides into two embryos.
3. In the case of fraternal twins, two separate eggs are released and fertilized independently.

V. Short Answer Questions 

Question 1.
Describe the microscopic structure of the testis in man.
Answer:

1. The testes of males are located in the scrotal sac, outside the abdominal cavity, because sperm production requires a temperature lower than normal body temperature.
2. Each testis is enclosed by a tough fibrous covering known as the tunica albuginea.
3. This covering extends inward and forms partitions called septa.
4. These septa divide the testis into nearly 250 lobules.
5. Every lobule contains 1 – 3 highly coiled seminiferous tubules.
6. The seminiferous tubules are lined by spermatogonia (germ cells) and Sertoli cells.
7. Spermatogonia develop into primary spermatocytes, which undergo meiosis to form spermatids.
8. Spermatids are transformed into mature sperm cells through spermiogenesis.
9. Sertoli cells provide nourishment to developing sperm and secrete Inhibin, which regulates FSH secretion.
10. Between the seminiferous tubules are Leydig (interstitial) cells.
11. Leydig cells synthesize and release androgens, mainly testosterone.
12. Seminiferous tubules open into the rete testis, which further connects to the vasa efferentia.
13. The vasa efferentia open into the epididymis, which is divided into the caput, corpus, and cauda regions.
14. The epididymis is highly coiled and serves as the site for sperm maturation and storage.

Question 2.
Describe the microscopic structure of the ovary of a woman.
Answer:

1. The ovaries are the primary female reproductive organs responsible for producing ova and female sex hormones.
2. A pair of ovaries is located in the lower abdominal region.
3. Each ovary is attached to the dorsal body wall by a fold of peritoneum called the mesovarium.
4. The outer surface of the ovary is covered by a simple cuboidal germinal epithelium.
5. Beneath this epithelium lies a dense connective tissue layer called the tunica albuginea.
6. The ovarian tissue is differentiated into an outer cortex and an inner medulla.
7. The medulla contains connective tissue, blood vessels, lymph vessels, and nerve fibers.
8. The cortex contains ovarian follicles at different stages of development.
9. Structures such as Graafian follicles, corpus luteum, and corpus albicans are found within the cortex.

Question 3.
Draw a labelled diagram of the male reproductive system.
Answer:

Question 4.
Draw a labelled diagram of the female reproductive system.
Answer:

Question 5.
What is spermatogenesis? Briefly describe the process of spermatogenesis in man.
Answer:
Spermatogenesis It is the process by which male gametes (sperms) are formed. In humans, this process begins at puberty.

Process :

1. Spermatogonial stem cells are present in the seminiferous tubules and divide repeatedly by mitosis.
2. Some spermatogonia differentiate into primary spermatocytes (2n = 46 chromosomes).
3. Each primary spermatocyte undergoes the first meiotic division to produce two haploid secondary spermatocytes (n = 23 chromosomes).
4. Secondary spermatocytes undergo the second meiotic division to form spermatids.
5. Each primary spermatocyte ultimately gives rise to four haploid spermatids.
6. Spermatids transform into mature spermatozoa through spermiogenesis.
7. Mature sperm heads remain embedded in Sertoli cells and are finally released by spermiation.
8. Hormones such as GnRH, FSH, and LH regulate spermatogenesis.
9. A mature sperm consists of a head, neck, middle piece, and tail.
10. The head bears an acrosome containing enzymes such as hyaluronidase that aid in fertilization.
11. The middle piece contains numerous mitochondria, which provide energy for sperm movement.

Question 6.
Describe the structure of a sperm cell with the help of a neat labelled diagram.
Answer:
A sperm cell is a microscopic, motile male gamete specialized for fertilization and enclosed by a plasma membrane.
It is divided into four major parts:
i) Head :

• Contains a haploid nucleus carrying genetic material.
• Covered by the acrosome, a cap-like structure.
• The acrosome contains enzymes that help the sperm penetrate the ovum during fertilization.

ii) Neck:

• A short connecting region between the head and middle piece.
• Contains centrioles involved in cell division after fertilization.

iii) Middle Piece:

• Contains numerous mitochondria arranged around the axial filament.
• Mitochondria generate ATP required for sperm motility.

iv) Tail (Flagellum):

• Long and slender structure responsible for locomotion.
• Propels the sperm through the female reproductive tract toward the ovum. Thus, the sperm is structurally adapted for movement and successful fertilization.

Question 7.
What is oogenesis? Give a brief account of oogenesis in a woman.
Answer:
Oogenesis is the process of formation of a mature female gamete (ovum). Unlike spermatogenesis, it begins during embryonic development.

1. Embryonic Stage :

• Millions of oogonia are formed in the fetal ovary.
• No new oogonia are produced after birth.
• Oogonia enter meiosis I and become primary oocytes.
• These primary oocytes remain arrested in prophase I.

2. Follicular Development:

• Each primary oocyte becomes surrounded by granulosa cells, forming a primary follicle.
• At puberty, about 60,000 – 80,000 primary follicles remain in each ovary.

3. Maturation:

• Primary follicles develop into secondary follicles and later into tertiary follicles.
• The tertiary follicle develops a fluid-filled cavity known as the antrum.

4. First Meiotic Division :

• The primary oocyte completes meiosis-I within the tertiary follicle.
• This unequal division produces a large secondary oocyte and a small first polar body.

5. Ovulation: The mature Graafian follicle ruptures and releases the secondary oocyte from the ovary.

6. Second Meiotic Division :

• Meiosis-II is completed only after fertilization.
• It produces a mature ovum and a second polar body.

Question 8.
Name the functions of the following :
(a) Corpus Luteum
(b) Fimbriae
(c) Acrosome
(d) Sperm Tail
Answer:
(a) Corpus Luteum :

• Secretes large amounts of progesterone.
• Progesterone maintains the endometrium and supports implantation and pregnancy.

(b) Fim briae :

• Finger-like projections present at the infundibulum of the fallopian tube.
• They help in collection of the ovum released from the ovary after ovulation.

(c) Acrosome:

• Cap-like structure present on the sperm head.
• Contains enzymes that help the sperm penetrate the coverings of the ovum during fertilization.

d) Sperm Tail:

• Responsible for sperm motility.
• Helps propel the sperm through the female reproductive tract toward the ovum.

VI. Long Answer Questions

Question 1.
Describe the Female Reproductive System of a woman with the help of a labelled diagram.
Answer:
The female reproductive organs are located in the pelvic cavity and include :
1) Ovaries :

• Ovaries are the primary female reproductive organs responsible for producing ova (female gametes) and female sex hormones.
• A pair of ovaries is situated on either side of the lower abdominal region.
• Each ovary is attached to the abdominal wall through a fold of peritoneum called the mesovarium.
• Every ovary consists of three main regions :

1. Germinal (ovarian) epithelium
2. Tunica albuginea
3. Stroma
The stroma is differentiated into an outer cortex and an inner medulla.

2. Fallopian Tubes:

• Each fallopian tube extends from the ovary to the uterus.
• The ovarian end of the tube is expanded into a funnel-shaped structure known as the infundibulum.
• The infundibulum bears finger-like projections called fimbriae.
• Fimbriae help in collecting the ovum released during ovulation.
• The fallopian tube is the usual site of fertilization and transports the ovum towards the uterus by peristaltic movements.

3. Uterus:

• The uterus is a single, hollow, muscular organ.
• It is located between the urinary bladder and rectum.
• It resembles an inverted pear and is richly supplied with blood vessels.
• The narrow lower region connecting the uterus to the vagina is called the cervix.
• The cervix and vagina together constitute the birth canal.
• The uterine wall consists of three layers: Outer Perimetrium, Middle Myometrium, Inner Endometrium
• The endometrium undergoes cyclic changes during the menstrual cycle.

4. Vagina:

• The vagina is a fibromuscular tube extending from the cervix to the vaginal opening.
• It is lined by non-keratinized stratified squamous epithelium and is highly vascular.

5. Vulva (External Genitalia):

• The term vulva (pudendum) refers to the external genital organs of the female.
• The vestibule is the region that contains the external openings of the urethra and vagina.
• The vaginal opening is partially covered by a thin mucous membrane called the hymen.
• The clitoris is homologous to the penis in males and contains erectile tissue.
• A fatty tissue pad covered by skin and pubic hair above the labia majora is called the mons pubis.

Accessory Reproductive Glands of Females: These include :
a) Bartholin’s glands,
b) Skene’s glands.

a) Bartholin’s glands:

• Also called Greater Vestibular Glands.
• They are located on either side of the vaginal opening and secrete mucus.

b) Skene’s Glands:

• Also known as Lesser Vestibular Glands.
• They are situated on the anterior wall of the vagina near the lower end of the urethra.

c) Mammary Glands:

• Mammary glands are paired structures composed of glandular tissue and varying amounts of fat.
• They contain alveoli, which produce and secrete milk after childbirth.
• Mammary ducts join to form a mammary ampulla, which opens into a lactiferous duct through which milk is delivered to the infant.

Question 2.
Describe the Male Reproductive System of a Man. Draw a Labelled Diagram of it. (AP MAR-16,17, 19,20,23,24)
Answer:
The male reproductive organs located in the pelvic region include:

1. Testes
2. Epididymis
3. Vas Deferens
4. Urethra
5. Penis
6. Accessory Glands

1. Testes :

• Testes are paired oval-shaped male primary reproductive organs.
• They are enclosed within a pouch called the scrotum, located outside the abdominal cavity.
• Sperm production requires a lower temperature; therefore, testes remain within the scrotum.
• The tunica albuginea forms septa that divide each testis into nearly 250 lobules.
• Each lobule contains 1 -3 highly coiled seminiferous tubules.
• Seminiferous tubules contain germinal epithelium and Sertoli cells. Germ cells produce sperm, while Sertoli cells nourish developing sperm.
• Testosterone regulates spermatogenesis and secondary sexual characteristics.
• Seminiferous tubules open into the rete testis, which continues into the vasa efferentia and epididymis

2. Epididymis:

• The epididymis is a long, tightly coiled tube located along the posterior side of each testis.
• Vasa efferentia open into the epididymis.
• It serves as a site for sperm maturation and temporary storage.

3. Vas Deferens :

• The vas deferens is a long, muscular tube.
• It begins from the tail of the epididymis, enters the abdominal cavity through the inguinal canal, and loops around the urinary bladder.

4. Urethra:

• The urethra originates from the urinary bladder and extends through the penis.
• It acts as a common passage for urine and semen.
• It opens to the exterior through the urethral meatus.

5. Penis:

• The penis functions as both a urinary organ and a copulatory organ that transfers sperm into the female reproductive tract.
• It consists of three columns of erectile tissue: Two corpora cavernosa and one corpus spongiosum
• The enlarged terminal part is the glans penis, covered by a loose fold of skin called the prepuce (foreskin).

6. Accessory Glands :
a) Seminal Vesicles :

• A pair of glands located behind the urinary bladder.
• Their secretion contains fructose, which provides energy for sperm.

b) Prostate Gland:

• Situated below the urinary bladder.
• Contributes about 15-30% of the seminal fluid.

c) Bulbourethral (Cowper’s) Glands :

• Located below the prostate gland.
• They secrete an alkaline fluid that lubricates and neutralizes the urethra during ejaculation.

Question 3.
Describe the Spermatogenesis and Oogenesis with Diagrammatic Representation.
Answer:
I) Spermatogenesis: Spermatogenesis is the process of sperm formation in the seminiferous tubules of the testes. It begins at puberty under the influence of GnRH.

1. Multiplication Phase: Immature germ cells called spermatogonia (2n = 46) divide repeatedly by mitosis.
2. Meiosis I: Primary spermatocytes undergo the first meiotic division to produce two haploid secondary spermatocytes.
3. Meiosis II: hi Secondary spermatocytes complete the second meiotic division to form four haploid spermatids.
4. Spermiogenesis: Spermatids differentiate into mature spermatozoa.
5. Spermiation: Mature sperm are released from Sertoli cells into the lumen of seminiferous tubules.

II) Oogenesis :
Oogenesis is the process of formation of a mature female gamete (ovum). It begins during embryonic life.

1. Embryonic Initiation: Millions of oogonia enter meiosis-I and become primary oocytes arrested in prophase I.
2. Follicular Development: Each primary oocyte is surrounded by granulosa cells to form a primary follicle. At puberty, about 60,000 – 80,000 follicles remain in each ovary.
3. Maturation: Primary follicles develop into secondary follicles and then tertiary follicles containing an antrum.
4. First Meiotic Division: The primary oocyte completes meiosis I, producing a large secondary oocyte and a first polar body.
5. Ovulation: The Graafian follicle ruptures and releases the secondary oocyte.
6. Second Meiotic Division: This division is completed only after fertilization, producing a haploid ootid (ovum) and a second polar body.

Question 4.
Explain the process of Fertilization and Implantation in Humans. Describe the major features of Embryonic Development at various months of pregnancy.
Answer:
1. Fertilization: Fertilization is the fusion of a sperm and ovum to form a zygote. It usually occurs in the ampullary region of the fallopian tube.

• Insemination and Transport: Semen is deposited in the vagina. Sperms travel through the cervix and uterus to reach the fallopian tube, where fertilization takes place.
• Contact and Entry: A sperm binds to the zona pellucida of the ovum and prevents entry of additional sperms.
• Acrosomal Reaction: Enzymes released from the acrosome help the sperm penetrate the ovum.
• Completion of Meiosis: Sperm entry stimulates completion of meiosis-II in the secondary oocyte, producing an ovum and second polar body.
• Zygote Formation: Fusion of male and female pronuclei results in a diploid zygote (2n). The sex of the baby depends on whether the fertilizing sperm carries an X or Y chromosome.

2. Implantation: Implantation is the process by which the developing embryo becomes attached to and embedded within the endometrium.

• Cleavage and Morula Formation: The zygote undergoes repeated mitotic divisions, producing blastomeres. The 8-16 cell stage is called the morula.
• Blastocyst Formation: The morula develops into a blastocyst composed of an outer trophoblast and inner cell mass.
• Attachment to Endometrium: The trophoblast attaches to the uterine endometrium.
• Embedding: The blastocyst becomes completely embedded within the uterine lining.
• Hormonal Support: Progesterone secreted by the corpus luteum maintains the endometrium and supports implantation.

3. Major Stages of Embryonic Development:

• End of First Month: The embryonic heart is formed.
• End of Second Month: Limbs and digits become visible.
• End of 12 Weeks (First Trimester): Most major organ systems are formed, and external genitalia become distinguishable.
• Fifth Month: Foetal movements can be felt, and hair appears on the head.
• End of 24 Weeks (Second Trimester): Fine body hair develops, eyelashes appear, and eyelids separate.
• End of Nine Months: The foetus becomes fully developed and ready for birth (parturition).

I. Multiple Choice Questions

Question 1.
Humans are ………………………….
1. Oviparous
2. Viviparous
3. Ovoviviparous
4. Parthenogenetic
Answer:
2. Viviparous

Question 2.
The reason behind the presence of testes outside the abdomen is :
1. To decrease the temperature up to 2°C to 2.5°C for spermatogenesis.
2. To increase the temperature up to 2°C to 2.5°C for spermatogenesis.
3. There is no sufficient space in abdominal cavity.
4. To prevent excessive production of sperms.
Answer:
1. To decrease the temperature up to 2°C to 2.5°C for spermatogenesis.

Question 3.
Which of the following depicts the correct pathway of transport of sperms?
1. Vasa Efferentia → Rete Testis → Vas Deference → Epididymis
2. Rete Testis → Epididymis → Vasa Efferentia → Vas Deference
3. Rete Testis → Vas Deference → Vasa Efferentia → Epididymis
4. Rete Testis → Vasa Efferentia → Epididymis → Vas Deferens
Answer:
4. Rete Testis → Vasa Efferentia → Epididymis → Vas Deferens

Question 4.
Which of the following acts as temporary endocrine tissue after ovulation in human females?
1. Corpus albicans
2. Corpus luteum
3. Graafian follicle
4. Tertiary follicle
Answer:
2. Corpus luteum

Question 6.
The correct sequence of milk passage in mammary gland, beginning from alveoli, would be:
1. Mammary tubules → Mammary ampulla → Mammary ducts → Lactiferous ducts
2. Lactiferous ducts → Mammary ducts → Mammary ampulla → Mammary tubules
3. Lactiferous ducts → Mammary ampulla → Mammary ducts → Mammary tubules
4. Mammary tubules → Mammary ducts → Mammary ampulla → Lactiferous ducts
Answer:
4. Mammary tubules → Mammary ducts → Mammary ampulla → Lactiferous ducts

Question 7.
Assertion: The seminal plasma along with the sperms constitute the semen.
Reason: For normal fertility, at least 40 per cent of ejaculated sperms must have normal shape and size, and at least 60 per cent of them must show vigorous motility. ,
1. If both assertion and reason are true and reason is the correct explanation of assertion.
2. If both assertion and reason are true but reason is not the correct explanation of assertion.
3. If assertion is true but reason is false.
4. If Assertion false and Reason is true.
Answer:
3. If assertion is true but reason is false.

Question 8.
The second meiotic division of oocyte is completed during
1. Childbirth
2. Puberty
3. Ovulation
4. Fertilization
Answer:
4. Fertilization

Question 9.
Most of the major organ systems in foetal stage are formed
1. By the end of 151 month
2. By the end of 2nd month
3. By the end of 3rd month
4. By the end of 3rd week
Answer:
3. By the end of 3rd month

Question 10.
The signal for foetal ejection reflex in human female originates from
1. Progesterone
2. Differentiation of mammary glands
3. Fully developed foetus and placenta
4. Sudden drop of oxytocin
Answer:
3. Fully developed foetus and placenta

Question 11.
The act of delivering a foetus at the end of pregnancy is called …………………….. .
1. Parturition
2. Gestation
3. Coitus
4. Lactation
Answer:
1. Parturition

II. Fill in the Blanks

1. Testes are situated outside the abdominal cavity within a pouch called ……………………….. .
Answer:
Scrotum

2. The seminiferous tubules of the testis open into the vasa efferentia through …………………. .
Answer:
Rete testis

3. The part of fallopian tube closer to the ovary with funnel-shaped structure called ……………………. .
Answer:
Infundibulum

4. The process of release of ovum from a mature follicle is called ………………………. .
Answer:
Ovulation

5. Ovulation is induced by a hormone called ………………………… .
Answer:
Luteinizing hormone (LH)

6. The uterine layer that exhibits strong contraction during delivery of the baby is ………………………….. .
Answer:
Myometrium.

7. The fusion of male and female gametes is called …………………………….. .
Answer:
Fertilization

8. The first menstruation is called ………………………….. .
Answer:
Menarche.

9. Zygote divides to form …………………………… which is implanted in uterus.
Answer:
Blastocyst

10. The structural and functional unit between foetus and uterus is called ………………………… .
Answer:
placenta

III. One Word Answer Questions

Question 1.
How many seminiferous tubules are present in every testicular lobule in which sperm are produced?
Answer:
1 to 3

Question 2.
Name the hormones that are synthesized and secreted by Leydig cells.
Answer:
Androgens

Question 3.
The fingerlike projections of the infundibulum of fallopian tube are called as?
Answer:
Fimbriae

Question 4.
What is the tiny finger-like structure which lies at the upper junction of the two labia minora above the urethral opening?
Answer:
Clitoris

Question 5.
Which layer undergoes cyclic changes in menstrual cycle?
Answer:
Endometrium

Question 6.
By the end of which month of gestation is the heart formed in a human embryo?
Answer:
By the end of the first month

Question 7.
The milk produced in the initial few’ days of lactation which is rich in antibodies called ?
Answer:
Colostrum

Question 8.
How many eggs do you think were released by the ovary of a female dog which gave birth to 6 puppies?
Answer:
6 (Six) eggs

Question 9.
What is the cessation of menstrual cycle called?
Answer:
Menopause

Objective Questions

Question 1.
In which type of reproduction are genetic variations commonly observed?
1. Schizogony
2. Sexual reproduction
3. Multiple fission
4. Budding
Answer:
2. Sexual reproduction

Question 2.
Which structure forms the outer covering of the ovary?
1. Mesovarium
2. Germinal epithelium
3. Columnar epithelium
4. Ciliated epithelium
Answer:
2. Germinal epithelium

Question 3.
Cleavage in human beings is classified as :
1. Equal
2. Holoblastic
3. Meroblastic
4. Determinate
Answer:
2. Holoblastic

Question 4.
What is the primary role of the epididymis?
1. Activation of the sperms only
2. Temporary storage of the sperms until they mature
3. Spermatogenesis and spermiogenesis
4. Nourishing of the sperms only
Answer:
2. Temporary storage of the sperms until they mature

Question 5.
What is the basic characteristic feature of sexual reproduction?
1. Fusion of two adult individuals
2. Fusion of male and female gametes produced by meiosis
3. Fusion of gametes produced by mitosis
4. Fusion of male and female haploid gametes produced by mitosis
Answer:
2. Fusion of male and female gametes produced by meiosis

Question 6.
Testes remain attached to the scrotal sac posteriorly through :
1. Dartos muscle
2. Spermatic cords
3. Gubernaculum
4. Rachis
Answer:
3. Gubernaculum

Question 7.
Meiosis takes place in :
1. Both (3) and (4)
2. Spermatogonia and oogonia
3. Primary and secondary oocytes
4. Primary and secondary spermatocytes
Answer:
1. Both (3) and (4)

Question 8.
Seminal plasma receives secretions from :
1. Bulbourethral glands
2. Seminal vesicles
3. Prostate gland
4. All of the above
Answer:
4. All the above

Question 9.
Which part of the fallopian tube is nearest to the ovary?
1. Cervix
2. Ampulla
3. Infundibulum
4. Isthmus
Answer:
3. Infundibulum

Question 10.
Which enzyme helps sperm penetrate the corona radiata and zona pellucida?
1. Citric acid
2. Hyaluronidase
3. Hydrochloric acid
4. Protease
Answer:
2. Hyaluronidase

Question 11.
Implantation in humans generally occurs on :
1. 12th day after copulation
2. 6th day after ovulation
3. 6th day after fertilization
4. 6th day after menstruation
Answer:
4. 6th day after menstruation

Question 12.
Which enzyme plays an important role during implantation?
1. Lipases
2. Amylases
3. Progesterone
4. Proteases
Answer:
4. Proteases

Question 13.
At what stage does the foetal heart begin to beat?
1. End of first trimester
2.2nd month
3. 4th week
4. 14th day
Answer:
3. 4th week

Question 14.
Which gland secretes the highest amount of fructose?
1. Cowper’s gland
2. Prostate gland
3. Tyson gland
4. Seminal vesicle
Answer:
4. Seminal vesicle

Question 15.
In mammals, failure of testes to descend into the scrotum is termed :
1. Castration
2. Impotency
3. Paedogenesis
4. Cryptorchidism
Answer:
4. Cryptorchidism

Question 16.
The vas deferens originates from :
1. Rete testis
2. Corpus epididymis
3. Caput epididymis
4. Cauda epididymis
Answer:
4. Cauda epididymis

Question 17.
Which accessory reproductive gland is unique to male mammals?
1. Prostate gland
2. All
3. Pineal gland
4. Bartholin’s gland
Answer:
1. Prostate gland

Question 18.
Seminal vesicle opens at the junction of:
1. Vas deferens and testis
2. Prostate and urethra
3. Prostate and vas deferens
4. Prostate and Cowper’s gland
Answer:
3. Prostate and vas deferens

Question 19.
Developing sperms receive nourishment from :
1. Connective tissue cells
2. Interstitial cells
3. None
4. Sertoli cells
Answer:
4. Sertoli cells

Question 20.
The egg released during ovulation in humans is at which stage?
1. Mature ovum stage
2. Secondary oocyte stage
3. Oogonial stage
4. Primary oocyte stage
Answer:
2. Secondary oocyte stage

Question 21.
The endocrine structure formed after ovulation from the ruptured Graafian follicle is:
1. Corpus albicans
2. Corpus luteum
3. Corpus striatum
4. Corpus callosum
Answer:
2. Corpus luteum

Question 22.
Which female structure is considered homologous to the male prostate gland?
1. Bulbourethral gland
2. Bartholin’s gland
3. Clitoris
4. None of the above
Answer:
4. None of the above

Question 23.
The luteal phase is also known as:
1. Secretory phase
2. Menstrual flow phase
3. Follicular phase
4. Proliferative phase
Answer:
1. Secretory phase

Question 24.
Which extraembryonic membrane prevents the embryo from drying out inside the uterus?
1. Allantois
2. Yolk sac
3. Chorion
4. Amnion
Answer:
4. Amnion

Question 25.
Which membrane contributes to the formation of the urinary bladder of the embryo?
1. Yolk sac
2. Chorion
3. Minion
4. Allantois
Answer:
4. Allantois

Question 26.
Spermatogenesis is mainly regulated by the influence of:
1. LH
2. ADH
3. STH
4. FSH
Answer:
4. FSH

Question 27.
Which statement is incorrect regarding oogenesis?
1. Growth phase
2. Equal meiotic division
3. Formation of polar bodies
4. Unequal meiotic division
Answer:
2. Equal meiotic division

Question 28.
Prostaglandins are synthesized from:
1. Carbohydrate
2. Steroid
3. Fatty acids
4. Amino acids
Answer:
3. Fatty acids

Question 29.
The embryo at the sixteen-cell stage is known as:
1. Blastomere
2. Gastrula
3. Morula
4. Blastula
Answer:
3. Morula

Question 30.
Which phase of the menstrual cycle normally continues for about 7-8 days?
1. Ovulatory phase
2. Menstruation
3. Follicular phase
4. Luteal phase
Answer:
3. Follicular phase

Question 31.
Corpus luteum and macula lutea share the common feature that they are:
1. Characterised by yellow colour
2. Source of hormones
3. Found in human ovaries
4. Contributory in maintaining pregnancy
Answer:
1. Characterised by yellow colour

Question 32.
Fertilin is produced and released by :
1. Epididymis
2. Testes
3. Egg surface
4. Sperm head tip
Answer:
3. Egg surface

Question 33.
The secretory phase of the menstrual cycle is alternatively termed :
1. Follicular phase and lasts for about 13 days
2. Follicular phase and lasts for about 6 days
3. Luteal phase and lasts for about 13 days
4. Luteal phase and lasts for about 6 days
Answer:
3. Luteal phase and lasts for about 13 days

Question 34.
The signals responsible for initiating parturition arise from:
1. Fully developed foetus only
2. Placenta as well as fully developed foetus
3. Oxytocin released from maternal pituitary
4. Placenta only
Answer:
2. Placenta as well as fully developed foetus

Question 35.
The second maturation division of the mammalian ovum takes place:
1. Until nucleus of sperm and ovum fuse
2. Shortly after ovulation before entry into fallopian tube
3. In Graafian follicle soon after first maturation division
4. Until after sperm has penetrated into ovum
Answer:
4. Until after sperm has penetrated into ovum

Question 36.
Following ovulation, the follicle transforms into :
1. Corpus callosum
2. Corpus cavemosum
3. Corpus luteum
4. Corpus albicans
Answer:
3. Corpus luteum

Question 37.
Bartholin’s glands are located :
1. On either side of vas deferens in humans
2. On either side of vagina in humans
3. On the reduced tail end of birds
4. On the sides of the head of some amphibians
Answer:
2. On either side of vagina in humans

Question 38.
What will be the consequence if the vas deferens is cut?
1. Sperms are non-nucleated
2. Spermatogenesis does not occur
3. Semen is without sperms
4. Sperms are nonmotile
Answer:
3. Semen is without sperms

Question 39.
Functional maturation of sperms occurs in :
1. Epididymis
2. Vagina
3. Oviduct
4. All of these
Answer:
1. Epididymis

Question 40.
Which hormone promotes the development of female secondary sexual characters?
1. Testosterone
2. Androgen
3. Estrogen
4. Progesterone
Answer:
3. Estrogen

Reviewing AP Inter 2nd Year Botany Study Material Chapter 6 Ecosystem Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Botany 6th Lesson Ecosystem Questions and Answers

IV. Very Short Answer Questions

Question 1.
Define an ecosystem.
Answer:

1. An ecosystem is the basic functional unit of the biosphere where organisms interact with one another as well as with their surrounding physical environment.
2. These interactions involve the transfer of energy and cycling of nutrients within the system. Examples: Pond, Lake.

Question 2.
Name any two decomposers found in a pond ecosystem.
Answer:
Common decomposers present in a pond ecosystem include :

1. Fungi
2. Bacteria
3. Flagellates

Question 3.
What is humus?
Answer:
Humus is a dark-coloured, amorphous organic substance formed during the decomposition of organic matter through the process of humification.

Question 4.
Mention any two climatic factors that affect the rate of decomposition.
Answer:
Two important climatic factors influencing decomposition are :

1. Temperature
2. Soil moisture.

Question 5.
What is meant by a trophic level?
Answer:
A trophic level refers to the feeding position occupied by an organism in a food chain based on the source from which it obtains food and energy.

Question 6.
What is an ecological pyramid?
Answer:
An ecological pyramid is a diagrammatic representation that illustrates the relationship among organisms at different trophic levels in terms of number, biomass, or energy.

V. Short Answer Questions

Question 1.
Describe the types and importance ecological pyramids.
Answer:
An ecological pyramid is a diagrammatic representation that illustrates the feeding and energy relationships among organisms at different trophic levels in an ecosystem. It generally has a broad base consisting of producers and a narrow top occupied by top consumers.

Types of Ecological Pyramids :
1. Pyramid of Numbers:

• Represents the number of individuals present at each trophic level.
• Generally remains upright. Example: Grassland ecosystem.
• May become inverted in certain ecosystems. Example: A single tree supporting numerous insects.

2. Pyramid of Biomass:

• Shows the total biomass (living matter) present at each trophic level.
• Usually upright in terrestrial ecosystems.
• Can be inverted in aquatic ecosystems where the biomass of fishes exceeds that of phytoplankton.

3. Pyramid of Energy:

• Depicts the amount of energy available at successive trophic levels.
• It is always upright and never inverted.
• Since energy is lost as heat at every trophic level (10% law), higher trophic levels possess progressively less energy.

Importance of Ecological Pyramids :

• Illustrates energy transfer Helps in understanding how energy moves through different trophic levels and flows the 10% law.
• Explains trophic relationships: Shows the relationship between producers and consumers in terms of number, biomass, and energy.
• Facilitates ecosystem comparison: Upright and inverted pyramids help compare different ecosystems such as grasslands and aquatic systems.
• Indicates ecosystem stability: Helps in understanding the balance, structure, and functioning of ecosystems.

Question 2.
Distinguish between gross primary productivity and net primary productivity.
Answer:

Question 3.
Explain the different steps involved in the process of decomposition.
Answer:

1. Decomposition is the breakdown of dead organic matter (detritus) into simpler inorganic substances such as carbon dioxide, water, and nutrients by decomposers.
2. It is predominantly an oxygen-dependent process and occurs through several stages.
3. The first stage is fragmentation, where detritivores like earthworms break detritus into smaller pieces, increasing the surface area available for microbial activity.
4. This is followed by leaching, in which water dissolves soluble nutrients and carries them into deeper soil layers.
5. The next stage is catabolism, where bacteria and fungi release enzymes that convert complex organic compounds into simpler substances.
6. Subsequently, humification occurs, resulting in the formation of humus, a dark-coloured amorphous substance.
7. Humus is resistant to further decomposition and serves as a nutrient reservoir.
8. Finally, mineralisation takes place, where microbes break down humus and release inorganic nutrients into the soil, making them available to plants.
9. Fragmentation, leaching and catabolism often occur simultaneously.
10. The rate of decomposition is influenced by factors such as temperature, moisture and the chemical composition of detritus.

Question 4.
Differentiate between grazing food chain and detritus food chain.
Answer:

VI. Long Answer Questions

Question 1.
Describe the components of an ecosystem.
Answer:

• An ecosystem is a functional unit of nature where living organisms interact with one another and with their surrounding environment.
• It consists of abiotic (non-living) and biotic (living) components, along with structural and – Wabr functional features.

Abiotic Components (Non-living): Abiotic factors include all physical and chemical elements that influence living organisms.
i) Physical and inorganic materials :

• Air supplies oxygen for respiration and carbon dioxide for photosynthesis.
• Water is essential for life processes.
• Soil provides minerals and support for plant growth.

ii) Dissolved substances:

• Nutrients such as nitrogen, phosphorus, and minerals occur in soil and water.
• These nutrients are absorbed by plants and transferred through food chains.

iii) Climatic factors:

• Sunlight, temperature, rainfall, humidity, and wind regulate photosynthesis, growth, and reproduction.
• Sunlight serves as the primary source of energy in most ecosystems.

2. Biotic Components (Living): Biotic components include all living organisms classified according to their role in energy transfer.
i) Producers (Autotrophs):

• Green plants, algae, and phytoplankton convert solar energy into chemical energy through photosynthesis.
• They form the foundation of food chains.

ii) Consumers (Heterotrophs):

• Depend on producers or other organisms for food.
• Primary consumers feed on plants.
• Secondary and tertiary consumers feed on other animals.

iii) Decomposers (Saprotrophs):

• Bacteria and fungi decompose dead plants, animals, and organic matter.
• They convert complex substances into simple nutrients and recycle them back to the environment.

3. Structural Features of an Ecosystem :

• Species composition: Refers to the variety and abundance of species present in an ecosystem. Greater diversity generally indicates higher stability.
• Stratification: Organisms are arranged in different vertical layers. For example, forests show canopy, shrub, and ground layers.

4. Functional Aspects of an Ecosystem :

• Productivity: Rate at which producers synthesize organic matter through photosynthesis.
• Decomposition: Breakdown of dead organic matter into simpler substances.
• Energy flow: Energy moves from the sun to producers and then to consumers in a unidirectional manner.
• Nutrient cycling: Continuous circulation of nutrients such as carbon, nitrogen, and phosphorus between living and non-living components.

Question 2.
Give an account of energy flow in an ecosystem.
Answer:
Flow of Energy in an Ecosystem :

1. The Sun is the ultimate source of energy for all ecosystems.
2. Solar energy is captured by plants and transferred through various trophic levels.
3. Less than 50% of the incoming solar radiation is photosynthetically active radiation (PAR).
4. Plants utilize only about 2-10% of PAR, which supports the entire living world.
5. All organisms depend directly or indirectly on producers for energy.
6. According to the First Law of Thermodynamics, energy can neither be created nor destroyed; it only changes from one form to another.
7. The Second Law of Thermodynamics states that some energy is lost as heat at every trophic level, reducing the amount available to the next level.
8. Energy transfer through trophic levels is known as energy flow.
9. Available energy decreases progressively at higher trophic levels.
10. When organisms die, their stored energy becomes available to decomposers.
11. Each trophic level possesses a certain amount of living material called the standing crop.
12. Standing crop represents biomass and may be expressed as fresh weight or dry weight, with dry weight being more accurate.

I. Multiple Choice Questions

Question 1.
An ecosystem can best be defined as :
1. A collection of similar species living in a habitat.
2. A group of plants and animals living together without interaction.
3. A functional unit where living organisms interact with each other and the environment.
4. The population of a single species in a given area.
Answer:
3. A functional unit where living organisms interact with each other and the environment.

Question 2.
Which of the following is not a natural ecosystem?
1. Desert
2. Forest
3. Aquarium
4. Lake
Answer:
3. Aquarium

Question 3.
Vertical distribution of different species occupying various levels ¡n an ecosystem is called:
1. Stratification
2. Speciation
3. Decomposition
4. Succession
Answer:
1. Stratification

Question 4.
The rate of biomass production per unit area and time is known as:
1. Decomposition
2. Productivity
3. Energy flow
4. Respiration
Answer:
2. Productivity

Question 5.
Net Primary Productivity (NPP) is calculated as:
1. GPP+R
2. GPP-R
3. R-GPP
4. GPP × R
Answer:
2. GPP-R

Question 6.
The process of breaking down complex organic matter into simple inorganic substances is known as :
1. Mineralization
2. Decomposition
3. Stratification
4. Catabolism
Answer:
2. Decomposition

Question 7.
The energy transfer from one trophic level to another follows the
1. 50% law
2. 25% law
3. 10% law
4. 90% law
Answer:
3. 10% law

Question 8.
In a terrestrial ecosystem, the major conduit for energy flow is the
1. Detritus food chain
2. Grazing food chain
3. Inverted pyramid
4. Microbial chain
Answer:
1. Detritus food chain

Question 9.
Which ecological pyramid is always upright?
1. Pyramid of numbers
2. Pyramid of biomass
3. Pyramid of energy
4. Pyramid of productivity
Answer:
3. Pyramid of energy

Question 10.
The pyramid of biomass in the sea is generally inverted because:
1. Phytoplankton have a higher biomass than that of fishes.
2. Fishes have more biomass than that of phytoplankton.
3. Energy flow in the sea is bidirectional.
4. Decomposers dominate the marine ecosystem.
Answer:
2. Fishes have more biomass than that of phytoplankton.

II. Fill in the Blanks

1. The natural interconnection of food chains make ………………………… .
Answer:
Food web

2. Each trophic level has a certain mass of living material at a particular time called …………………………. .
Answer:
Standing crop

3. …………………………… is the process through which water-soluble inorganic nutrients go down into the soil horizon and get precipitated as unavailable salts.
Answer:
Leaching

Question 4.
Common decomposers in pond ecosystems are ……………………………….. .
Answer:
Bacteria, fungi, and flagellates

5. Measurement of biomass in terms of ……………………….. weight is more accurate
Answer:
Dry

6. In aquatic ecosystems, the limiting factor for the productivity is ………………………….. .
Answer:
Light

7. The rate of decomposition is slower if detritus is rich in lignin and ……………………….. .
Answer:
Chitin

8. Only about ………………………….. percent of the incident solar radiation is photosynthetically active radiation (PAR).
Answer:
Less than 50

9. ………………………… play a vital role in the ecosystem but not given any place in ecological pyramids.
Answer:
Saprophytes

10. Plants are called …………………………. because they fix carbon dioxide.
Answer:
Producers

III. One Word Answer Questions

Question 1.
What is the natural structural and functional unit where living organisms interact with their environment?
Answer:
Ecosystem

Question 2.
What do we call organisms that prepare their own food using sunlight?
Answer:
Producers

Question 3.
Which term describes the rate of production of biomass or organic matter per unit area over time?
Answer:
Productivity

Question 4.
Which organisms break down dead organic matter into inorganic nutrients?
Answer:
Decomposers

Question 5.
What is the dark, amorphous substance formed during the process of humification?
Answer:
Humus

Question 6.
What is the primary source of energy for all ecosystems on Earth?
Answer:
Sun

Question 7.
What is the sequence of organisms through which energy is transferred in an ecosystem called?
Answer:
Food chain

Question 8.
Which trophic level is occupied by herbivores in a food chain?
Answer:
Second trophic level

Question 9.
Which ecological pyramid is always upright and never inverted?
Answer:
Pyramid of Energy

Question 10.
Which process releases inorganic nutrients from humus through microbial activity?
Answer:
Mineralisation

Objective Questions

Question 1.
The interaction between organisms and their physical surroundings leads primarily to:
1. Species extinction
2. Formation of functional units
3. Random associations
4. Only energy loss
Answer:
2. Formation of functional units

Question 2.
A pond is regarded as a self-sustaining ecosystem because it exhibits components such as productivity, energy flow, and:
1. Mutation
2. Decomposition
3. Evolution
4. Stratification
Answer:
2. Decomposition

Question 3.
The layered arrangement of trees, shrubs, and grasses in a forest ecosystem is known as:
1. Biomagnification
2. Food chain
3. Stratification
4. Trophic collapse
Answer:
3. Stratification

Question 4.
In pond ecosystems, the chief autotrophic organisms are:
1. Earthworms
2. Phytoplankton and algae
3. Fishes
4. Zooplankton
Answer:
2. Phytoplankton and algae

Question 5.
Consumers in a pond ecosystem are organisms that:
1. Decompose matter
2. Feed on producers or other consumers
3. Produce their own food
4. Fix nitrogen
Answer:
2. Feed on producers or other consumers

Question 6.
Decomposers primarily convert organic matter into:
1. Proteins
2. Lipids
3. Inorganic substances
4. Complex polymers
Answer:
3. Inorganic substances

Question 7.
Energy flow in an ecosystem is considered unidirectional because it:
1. Remains constant
2. Moves only upward
3. Flows and is lost as heat
4. Cycles continuously
Answer:
3. Flows and is lost as heat

Question 8.
Productivity is generally expressed in units such as:
1. kg/hour
2. mol/L
3. g/m²/year
4. m/s
Answer:
3. g/m²/year

Question 9.
Gross Primary Productivity (GPP) includes the total organic matter produced along with:
1. Decomposition
2. Respiration losses
3. Secondary production
4. Only stored biomass
Answer:
2. Respiration losses

Question 10.
Net Primary Productivity (NPP) represents the biomass available to:
1. Only decomposers
2. Only bacteria
3. Heterotrophs
4. Only producers
Answer:
3. Heterotrophs

Question 11.
Although oceans occupy nearly 70% of Earth’s surface, their productivity is comparatively low mainly due to:
1. High salinity
2. Excess sunlight
3. Lack of nutrients
4. High oxygen
Answer:
3. Lack of nutrients

Question 12.
Biomass production by heterotrophic organisms is referred to as:
1. Parasites
2. Producers
3. Consumers
4. Decomposers
Answer:
3. Consumers

Question 13.
In the decomposition process, fragmentation is mainly performed by:
1. Carnivores
2. Parasites
3. Detritivores
4. Plants
Answer:
3. Detritivores

Question 14.
The downward transport of nutrients into the soil due to water is called:
1. Water action
2. Photosynthesis
3. Chemical reactions
4. Evaporation
Answer:
1. Water action

Question 15.
During decomposition, catabolism is associated with:
1. Energy storage
2. Reproduction
3. Breaking down substances
4. Building complex molecules
Answer:
3. Breaking down substances

Question 16.
Which substance is produced as a result of humification?
1. Proteins
2. Humus
3. Lipids
4. Glucose
Answer:
2. Humus

Question 17.
Humus is characterized by being:
1. Rich in microbes
2. Inorganic
3. Resistant to decomposition
4. Highly degradable
Answer:
3. Resistant to decomposition

Question 18.
Decomposition proceeds more rapidly when detritus is rich in:
1. Chitin
2. Wax
3. Nitrogen
4. Lignin
Answer:
3. Nitrogen

Question 19.
Warm and moist environmental conditions accelerate decomposition by:
1. Preventing leaching
2. Enhancing microbial activity
3. Slowing microbial activity
4. Stopping reactions
Answer:
2. Enhancing microbial activity

Question 20.
The rate of decomposition generally declines under :
1. Increase respiration
2. Increase decomposition
3. Decrease decomposition
4. Have no effect
Answer:
3. Decrease decomposition

Question 21.
Plants can utilize only a small fraction of solar radiation because :
1. It is reflected by soil
2. Only PAR is useful
3. It is converted to heat
4. It is absorbed by animals
Answer:
2. Only PAR is useful

Question 22.
Approximately what percentage of PAR is captured by plants?
1. 80 – 90%
2. 50 – 70%
3. 2 – 10%
4. 20 – 30%
Answer:
3. 2 – 10%

Question 23.
Producers are important in ecosystems because they :
1. Consume energy
2. Reduce oxygen
3. Fix solar energy
4. Decompose matter
Answer:
3. Fix solar energy

Question 24.
Primary consumers are mainly
1. Decomposers
2. Carnivores
3. Omnivores
4. Herbivores
Answer:
4. Herbivores

Question 25.
The grazing food chain originates from:
1. Carnivores
2. Producers
3. Detritus
4. Decomposers
Answer:
2. Producers

Question 26.
The detritus food chain originates from:
1. Omnivores
2. Dead organic matter
3. Live plants
4. Herbivores
Answer:
2. Dead organic matter

Question 27.
Decomposers are commonly known as saprotrophs because they:
1. Fix nitrogen
2. Store nutrients
3. Decompose organic matter
4. Produce sap
Answer:
3. Decompose organic matter

Question 28.
Food webs are formed due to:
1. Absence of consumers
2. Interconnection of food chains
3. Single feeding relationships
4. Lack of producers
Answer:
2. Interconnection of food chains

Question 29.
Producers occupy which trophic level in a food chain?
1. Third trophic level
2. First trophic level
3. Fourth trophic level
4. Second trophic level
Answer:
2. First trophic level

Question 30.
Herbivores are placed in which trophic level?
1. Fourth level
2. First level
3. Second level
4. Third level
Answer:
3. Second level

Question 31.
Energy availability decreases at higher trophic levels mainly because of:
1. Increased consumption
2. Storage
3. Heat loss
4. Transfer efficiency
Answer:
3. Heat loss

Question 32.
The term “standing crop” refers to:
1. Decomposition rate
2. Number of crops harvested
3. Biomass at a given time
4. Productivity rate
Answer:
3. Biomass at a given time

Question 33.
Biomass estimation is more accurate when measured as dry weight because:
1. It simplifies counting
2. It removes water variability
3. It increases value
4. It is lighter
Answer:
2. It removes water variability

Question 34.
According to the 10% law:
1. Energy is constant
2. 90% energy is transferred
3. Only 10% energy is transferred
4. Energy increases upward
Answer:
3. Only 10% energy is transferred

Question 35.
The number of trophic levels in an ecosystem is mainly restricted by:
1. Oxygen
2. Water
3. Energy loss
4. Space
Answer:
3. Energy loss

Question 36.
Ecological pyramids depict relationships based on:
1. Only biomass
2. Energy, biomass, number
3. Only energy
4. Only number
Answer:
2. Energy, biomass, number

Question 37.
The base of an ecological pyramid is occupied by:
1. Carnivores
2. Producers
3. Consumers
4. Decomposers
Answer:
2. Producers

Question 38.
Which ecological pyramid is never inverted?
1. Variable
2. Upright
3. Inverted
4. Irregular
Answer:
2. Upright

Question 39.
In marine ecosystems, the biomass pyramid often appears inverted because:
1. Decomposers dominate
2. Fish biomass is higher
3. Producers dominate
4. Energy flow is cyclic
Answer:
2. Fish biomass is higher

Question 40.
Ecological pyramids in most ecosystems are upright mainly because:
1. Consumers dominate
2. Energy increases upward
3. Producers are more abundant
4. Producers are fewer
Answer:
3. Producers are more abundant

Question 41.
Humans are generally categorized as:
1. Producers
2. Only herbivores
3. Omnivores
4. Only carnivores
Answer:
3. Omnivores

Question 42.
Which of the following is not represented in ecological pyramids?
1. Consumers
2. Herbivores
3. Decomposers
4. Producers
Answer:
3. Decomposers

Question 43.
In forest ecosystems, stratification minimizes competition among plants by:
1. Eliminating weaker species
2. Allowing species to occupy different vertical levels
3. Preventing decomposition
4. Increasing energy loss
Answer:
2. Allowing species to occupy different vertical levels

Question 44.
Autotrophs in pond ecosystems synthesize organic matter using :
1. Thermal energy
2. Solar energy
3. Mechanical energy
4. Chemical energy
Answer:
2. Solar energy

Question 45.
Net Primary Productivity (NPP) mainly denotes :
1. Energy lost in decomposition
2. Energy used in respiration
3. Total biomass
4. Growth rate of plants
Answer:
2. Energy used in respiration

Question 46.
Earthworms are called farmers’ friends because they improve soil fertility through:
1. Increasing temperature
2. Breaking down organic matter
3. Producing oxygen
4. Fixing nitrogen
Answer:
2. Breaking down organic matter

Question 47.
Humus serves as a nutrient reservoir because it is:
1. Rich in oxygen
2. Colloidal in nature and resistant to decomposition
3. Easily degradable
4. Water-soluble
Answer:
2. Colloidal in nature and resistant to decomposition

Question 48.
The decomposition rate in an ecosystem is strongly influenced by:
1. Population density
2. Chemical composition of detritus
3. Light intensity
4. Wind speed
Answer:
2. Chemical composition of detritus

Question 49.
Lignin-rich detritus decomposes slowly because:
1. It absorbs oxygen
2. It resists microbial degradation
3. It contains excess nitrogen
4. It is water-soluble
Answer:
2. It resists microbial degradation

Question 50.
In terrestrial ecosystems, energy primarily moves through the:
1. Food web
2. Detritus food chain
3. Grazing food chain
4. Pyramid of energy
Answer:
2. Detritus food chain

Question 51.
Grazing food chains dominate aquatic ecosystems because:
1. Consumers are few
2. Producers are directly consumed by herbivores
3. Decomposers are absent
4. Detritus is abundant
Answer:
2. Producers are directly consumed by herbivores

Question 52.
The number of trophic levels remains limited because:
1. Consumers are few
2. Energy is lost at each transfer
3. Biomass increases upward
4. Producers are limited
Answer:
2. Energy is lost at each transfer

Question 53.
A pyramid of numbers may become inverted when:
1. Energy flow increases
2. A single large producer supports many consumers
3. Small producers support fewer consumers
4. Decomposers dominate
Answer:
2. A single large producer supports many consumers

Question 54.
The biomass pyramid in aquatic ecosystems is inverted because:
1. Producers have high biomass
2. Consumers reproduce slowly
3. Producers have low standing biomass but high turnover
4. Energy flow is reversed
Answer:
3. Producers have low standing biomass but high turnover

Question 55.
The pyramid of energy always remains upright due to:
1. Increased biomass
2. Energy recycling
3. Loss of energy as heat at each trophic level
4. Constant energy supply
Answer:
3. Loss of energy as heat at each trophic level

Question 56.
Saprotrophs play a major role in ecosystems because they:
1. Consume producers
2. Recycle nutrients by decomposition
3. Produce organic matter
4. Fix nitrogen
Answer:
2. Recycle nutrients by decomposition

Question 57.
Ecological pyramids have limitations because they:
1. Show decomposition
2. Do not account for food webs
3. Include all organisms
4. Show exact biomass
Answer:
2. Do not account for food webs

Question 58.
Why are decomposers generally excluded from ecological pyramids?
1. They do not consume energy
2. They are absent in ecosystems
3. They operate across multiple trophic levels
4. They are autotrophs
Answer:
3. They operate across multiple trophic levels

Question 59.
Biomass is usually expressed as dry weight instead of fresh weight because:
1. Dry weight is easier to measure
2. Water content varies greatly among organisms
3. Water is insignificant
4. Dry weight is higher
Answer:
2. Water content varies greatly among organisms

Question 60.
Energy flow in ecosystems is said to be irreversible mainly because:
1. Producers dominate
2. Nutrients are reused
3. Energy dissipates as heat
4. Energy cycles continuously
Answer:
3. Energy dissipates as heat

Question 61.
If energy transfer efficiency between trophic levels increased greatly, what would happen to the number of trophic levels?
1. Remain unchanged
2. Increase as more energy becomes available
3. Become zero
4. Decrease due to instability
Answer:
2. Increase as more energy becomes available

Question 62.
Excessive accumulation of detritus in an ecosystem suggests that:
1. Mineralisation is rapid
2. Catabolism is enhanced
3. Decomposition rate is reduced
4. Fragmentation is high
Answer:
3. Decomposition rate is reduced

Question 63.
An increase in lignin content of plant litter would cause nutrient cycling to:
1. Remain unaffected
2. Become irregular
3. Decrease due to slow decomposition
4. Increase rapidly
Answer:
3. Decrease due to slow decomposition

Question 64.
The greatest energy loss in an ecosystem occurs through:
1. Food web formation
2. Nutrient cycling
3. Respiration at each trophic level
4. Photosynthesis
Answer:
3. Respiration at each trophic level

Question 65.
What is the Immediate effect of completely removing herbivores from a grazing food chain?
1. Collapse of decomposers
2. Increase in carnivores
3. Increase in plant biomass
4. Decrease in producers
Answer:
3. Increase in plant biomass

Question 66.
Secondary consumers obtain energy indirectly from producers through:
1. Parasites
2. Herbivores
3. Decomposers
4. Detritus
Answer:
2. Herbivores

Question 67.
Long food chains are uncommon in nature primarily because :
1. Producers are limited
2. Decomposers are absent
3. Energy loss increases with each transfer
4. Consumers dominate
Answer:
3. Energy loss increases with each transfer

Question 68.
A highly productive ecosystem is typically characterized by:
1. Reduced nutrient cycling
2. Low biodiversity
3. High rate of biomass production
4. Low energy flow
Answer:
3. High rate of biomass production

Question 69.
A noticeable decrease in temperature within an ecosystem is most likely to result in:
1. Increased productivity
2. Faster decomposition
3. Increased mineralisation
4. Slower decomposition
Answer:
4. Slower decomposition

Question 70.
A detritus-based ecosystem becomes dominant when:
1. Consumers dominate
2. Dead organic matter accumulation is high
3. Producers are absent
4. Live plant consumption is high
Answer:
2. Dead organic matter accumulation is high

Question 71.
Ecological pyramids do not accurately represent omnivores because they:
1. Are producers
2. Occupy multiple trophic levels simultaneously
3. Consume plants
4. Decompose matter
Answer:
2. Occupy multiple trophic levels simultaneously

Question 72.
If trophic-level energy transfer were 100%, ecosystems would theoretically:
1. Support infinite trophic levels
2. Stop functioning
3. Collapse
4. Lose energy rapidly
Answer:
1. Support infinite trophic levels

Question 73.
Multiple feeding links within a food web help in:
1. Reduced biomass
2. Energy loss
3. Greater ecosystem resilience
4. Reduced productivity
Answer:
3. Greater ecosystem resilience

Question 74.
Elimination of top carnivores from an ecosystem is most likely to cause:
1. No change
2. Increase in herbivore population
3. Stable system
4. Decrease in producers
Answer:
2. Increase in herbivore population

Question 75.
The primary reason for the inverted biomass pyramid in aquatic ecosystems is:
1. Absence of decomposers
2. Rapid turnover of phytoplankton
3. High producer biomass
4. Low consumer population
Answer:
2. Rapid turnover of phytoplankton

Reviewing AP Inter 2nd Year Botany Study Material Chapter 5 Biotechnology Principles, Processes and Applications Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Botany 5th Lesson Biotechnology Principles, Processes and Applications Questions and Answers

IV. Very Short Answer Questions

Question 1.
Define biotechnology.
Answer:
Biotechnology is a branch of science that makes use of microorganisms, living cells, or their components at an
industrial level to produce useful products and services that benefit human fife and welfare.

Question 2.
What are molecular scissors? Where are they obtained from?
Answer:

1. Molecular scissors refer to restriction enzymes that cut DNA at specific recognition sites.
2. These enzymes are naturally isolated from bacteria.

Question 3.
What is EcoRI? How does it function?
Answer:

1. EcoRI is a restriction endonuclease obtained from the bacterium Escherichia coli.
2. It recognizes the specific DNA sequence 5′ GAATTC 3′ and cleaves the DNA between G and A.

Question 4.
What are cloning vectors? Give an example.
Answer:
1. Cloning vectors are DNA molecules used to carry and multiply foreign DNA fragments inside a host cell.
2. Examples include plasmids, bacteriophages, cosmids, and artificial chromosomes.

Question 5.
What is recombinant DNA?
Answer:
Recombinant DNA (rDNA) is a hybrid DNA molecule formed by joining a desired DNA fragment with another DNA molecule using the enzyme DNA ligase.

Question 6.
What is the full form of PCR? How is it useful in biotechnology? [AP MAR-23,25]
Answer:
1- PCR stands for Polymerase Chain Reaction.
2. PCR is widely used in:

• DNA cloning
• Gene amplification
• DNA fingerprinting

Question 7.
What is downstream processing? [AP MAR-17,19]
Answer:
The process of separating, purifying, and preparing a product for commercial use after its production is known as downstream processing.

Question 8.
How can one visualize DNA on an Agar gel? [AP MAR-15,20]
Answer:
DNA fragments separated on agarose gel can be visualized by staining them with ethidium bromide and then exposing the gel to ultraviolet (UV) light.

Question 9.
How can you differentiate exonucleases from endonucleases? [AP MAR-24]
Answer:

1. Exonucleases: Remove nucleotides one by one from the ends of DNA molecules.
2. Endonucleases: Cut DNA internally at specific sites within the DNA strand.

Question 10.
Write any two beneficial aspects of Genetically Modified plants.
Answer:

1. Reduced use of pesticides: Genetically modified plants can be made resistant to insect pests, thereby reducing the need for chemical pesticides. Example: Bt crops.
2. Improved nutritional quality: Genetic modification can enhance the nutritional value of crops. Example: Golden Rice enriched with Vitamin A (β-carotene).

V. Short Answer Questions

Question 1.
Give brief account of amplification of gene of interest using PCR.
Answer:

1. PCR stands for Polymerase Chain Reaction.
2. It is a technique used to produce a large number of copies of a desired DNA segment in vitro.
3. The process requires two sets of primers (short synthetic oligonucleotides complementary to specific regions of DNA), DNA polymerase enzyme, free nucleotides, and template DNA.
4. During PCR, primers bind to the target DNA sequence, and DNA polymerase synthesizes new DNA strands using the available nucleotides and the original DNA as a template.
5. Repeated cycles of DNA replication result in exponential amplification of the target DNA. After several cycles, millions to billions of copies of the desired DNA fragment can be produced.
6. This amplification is made possible by the use ofa thermostable DNA polymerase, such as Taq polymerase, isolated from the bacterium Thermus aquaticus. This enzyme remains active even at the high temperatures required during the process.
7. The amplified DNA fragment can then be inserted into a suitable vector for cloning or used for various molecular biology applications.
8. PCR-based gene amplification is also widely used in DNA fingerprinting, where DNA fragment patterns are analyzed for identification purposes.

Question 2.
What is a bioreactor? Describe briefly the stirring type of bioreactor?
Answer:

1. Bioreactors are large vessels, generally having a capacity of 100-1000 litres, used for carrying out biological processes on a large scale.
2. In these vessels, raw materials are converted into used products such as enzymes, antibiotics, vaccines, and other biomolecules with the help of microorganisms, plant cells or animal cells.
3. A bioreactor provides ideal conditions required for maximum product formation, such as optimum temperature, pH, substrate concentration, salts, vitamins, and oxygen supply.
4. The stirred-tank bioreactor is usually cylindrical in shape and is designed to ensure proper mixing of the contents.
5. Continuous stirring helps in uniform distribution of nutrients and efficient oxygen supply throughout the culture medium.

6. A stirred-tank bioreactor generally consists of:

• Agitator (stirring) system
• Oxygen delivery system
• Foam control system
• Temperature regulation system
• pH monitoring and control system
• Sampling outlet for withdrawing small quantities of culture at regular intervals.

Question 3.
Discuss different methods of insertion of recombinant DNA into the Host cell?
Answer:
1. Introduction through competent cells: Recombinant DNA can be introduced into competent bacterial cells by keeping them on ice, exposing them briefly to 42°C (heat shock), and then returning them to ice. This facilitates uptake of recombinant DNA.

2. Microinjection Method: In this method, recombinant DNA is directly injected into the nucleus of an animal cell using fine microscopic needles called microneedles.

3. Gene Gun (Biolistic) Method: This technique is mainly used for plant cells. Tiny particles of gold or tungsten coated with DNA are fired into cells at high velocity to deliver the recombinant DNA.

4. Vector-Mediated Transfer: Disarmed pathogens are used as vectors. When these vectors infect host cells, they transfer the recombinant DNA into the host cell where it can be expressed.

Question 4.
Write a short note on Bt cotton. [Ap MAR – 25]
Answer:

1. Bt cotton is a genetically modified (GM) cotton variety developed to provide protection against insect pests, particularly bollworms.
2. It is produced by introducing specific genes obtained from the bacterium Bacillus thuringiensis (Bt) into cotton plants.
3. This bacterium synthesizes insecticidal proteins that are effective against several groups of insects, including Lepidopterans (tobacco budworm, bollworm, armyworm), Coleopterans (beetles) and Dipterans (flies and mosquitoes).
4. During a particular stage of bacterial growth, Bt produces protein crystals that contain a toxic insecticidal protein.
5. The Bt toxin is initially present in an inactive form known as a protoxin. When an insect feeds on the plant, the alkaline pH of its gut converts the protoxin into an active toxin.
6. Most Bt toxins are specific to particular insect groups. These toxins are encoded by Cry genes. For example, Cry IAc and Cry IIAb provide resistance against cotton bollworm, while Cry IAb is effective against corn borer.

Question 5.
Explain the process of RNA interference.
Answer:
RNA interference (RNAi) is a natural biological mechanism in eukaryotic organisms that functions as a cellular defence system. It suppresses the expression of a specific gene by preventing the corresponding mRNA from producing a protein.

Steps involved :

• Entry of dsRNA: The process begins when double-stranded RNA (dsRNA) enters the cell. This dsRNA is complementary to the target mRNA and may originate from viruses, transposons or experimental introduction.
• Formation of complementary RNA strands: In biotechnology, genes are introduced in such a way that both sense RNA and antisense RNA are produced. These complementary strands pair with each other to form dsRNA.
• Activation of the RNAi pathway: The dsRNA activates the RNA interference machinery, which cuts the dsRNA into small RNA fragments. These fragments help identify and target the matching mRNA molecule.
• Silencing of mRNA: The target mRNA is cleaved or degraded, preventing it from being translated into a protein.
• Protection of the host organism: Since the harmful protein is not produced, disease- causing organisms such as the nematode Meloidogyne incognita are unable to survive effectively. This protects the host plant from infection and damage.

VI. Long Answer Questions

Question 1.
Explain briefly the various processes of Recombinant DNA Technology. [AP MAR-16,17,24,25]
Answer:
Steps involved in Recombinant DNA Technology :
1. Isolation of DNA:

• DNA serves as the hereditary material in living organisms.
• It is enclosed within the cell and surrounded by various cellular components.
• Cell walls are broken down using enzymes such as lysozyme and cellulase to release cellular contents.
• Membranes, proteins, and RNA are removed with the help of detergents and enzymes like ribonuclease.
• Pure DNA is finally precipitated by adding ethanol.

2. Fragmentation of DNA: The purified DNA is cut into smaller fragments using restriction enzymes. This produces DNA pieces of different lengths.
3. Isolation of Desired DNA Fragment: The required DNA fragments are separated using agarose gel electrophoresis. Since DNA carries a negative charge, it migrates through the gel, and the desired fragment is recovered from the gel.
4. Amplification of the Desired Gene by PCR: In Polymerase Chain Reaction (PCR), numerous copies of the selected DNA fragment are produced in vitro using primers and DNA polymerase. Repeated cycles generate millions to billions of copies.

5. Ligation of the DNA Fragment into a Vector: This step requires both a vector DNA and the desired DNA fragment.

• The vector and source DNA are cut using the same restriction enzyme to generate compatible sticky ends.
• The desired gene is then joined to the vector with the help of DNA ligase, resulting in the formation of recombinant DNA

6. Introduction of rDNA into the Host Cell: Recombinant DNA can be introduced into host cells through different methods.

• Host cells can be made competent and exposed to recombinant DNA under suitable conditions to facilitate uptake.
• In microinjection, recombinant DNA is directly injected into the nucleus of an animal cell.
• In the gene gun (biolistic) method, DNA-coated gold or tungsten particles are fired into plant cells.

7. Production of the Desired Gene Product: Once recombinant DNA enters a cloning vector and host cell, the foreign DNA replicates and expresses itself, producing the required product.

8. Downstream Processing: After biosynthesis is complete, the product undergoes processing before commercial use. This includes separation, purification, and formulation of the final product.

Question 2.
Give a brief account of the tools of Recombinant DNA Technology.
Answer:
Tools of Recombinant DNA Technology: The major tools used in recombinant DNA technology are:
1. Restriction Enzymes
2. Polymerase Enzymes
3. Ligases
4. Vectors
5. Host Organisms

1. Restriction Enzymes: Restriction enzymes belong to a broader group of enzymes called nucleases.

• Exonucleases: These enzymes remove nucleotides sequentially from the ends of DNA molecules.
• Endonucleases: These enzymes cleave DNA at specific internal recognition sites. Each restriction endonuclease identifies a particular palindromic sequence.

Example: EcoRI recognizes the sequence 51 GAATTC 3′ and cuts between G and A.
5′ G A A T T C 3′
3′ C T T A A G 5′

2. Polymerase Enzymes:

• DNA polymerase is used in PCR to synthesize multiple copies of a target DNA sequence.
• Through repeated cycles, a very large number of DNA copies can be produced.
• Amplification is carried out using Taq polymerase, which remains active even at high temperatures.
• The amplified DNA fragment can subsequently be inserted into a vector for cloning.

3. Ligases :

• DNA ligase joins the ends of vector DNA and the desired DNA fragment through covalent bonds.
• This results in the formation of a circular recombinant DNA molecule.

4. Vectors: Vectors are DNA molecules that carry foreign DNA into a suitable host cell.

• Function: They help in the multiplication and maintenance of foreign DNA.
• Examples: Plasmids, Bacteriophages, Cosmids

Properties of Cloning Vectors:

• They should possess a relatively low molecular weight.
• They must contain one or more unique restriction sites.
• They should be capable of autonomous replication inside the host cell.
• They should possess a selectable marker for identifying transformed cells.

5. Host Organisms: A suitable and competent host organism is essential for the successful introduction, replication, and expression of recombinant DNA.

I. Multiple Choice Questions

Question 1.
Being a negatively charged molecule, DNA in Electrophoresis moves towards
1. Anode
2. Cathode
3. Equator
4. None of the above
Answer:
1. Anode

Question 2.
Which of the following are used in gene cloning?
1. Ribosomes
2. Plasmids
3. Mesosomes
4. Histones
Answer:
2. Plasmids

Question 3.
What is the function of restriction enzymes? ‘
1. Restrict the elongation of DNA
2. Amplify the DNA molecules
3. Cut the DNA at specific locations
4. Separate the DNA fragments based on length
Answer:
3. Cut the DNA at specific locations

Question 4.
Agarose extracted from the seaweeds is used in
1. Downstream Processing
2. DNA Isolation
3. PCR
4. Electrophoresis
Answer:
4. Electrophoresis

Question 5.
Which of following bacterium is used for production of transgenic plants
1. Agrobacterium
2. Staphylococcus
3. Pseudomonas
4. Thiobacillus
Answer:
1. Agrobacterium

Question 6.
In genetic engineering, antibiotic resistance gene is used as
1. PCR
2. Selectable marker
3. Replicator
4. Vector
Answer:
2. Selectable marker

Question 7.
The technique of producing large number of plants in a very short time is known as
1. Gene transfer
2. Conventional bree
3. Micropropagation
4. Somatic Hybridisation
Answer:
3. Micropropagation

Question 8.
Somatic hybrids are formed by
1. Meristem Culture
2. RNA interference
3. Microinjection
4. Protoplast fusion
Answer:
4. Protoplast fusion

Question 9.
Which part of the plant is grown in vitro to obtain virus-free plants
1. Meristem
2. Ovule
3. Anther
4. Leaf
Answer:
1. Meristem

Question 10.
Meloidogyne incognita, which infects the roots of a tobacco plant, is a
1. Bacterium
2. Virus
3. Algae
4. Nematode
Answer:
4. Nematode

II. Fill in the Blanks

1. Large volume of culture can be processed by using ………………………. .
Answer:
Bioreactors.

2. Genes are located on long molecules ……………………….. of intertwined with histone proteins.
Answer:
DNA

3. ……………………., in animal cells have the ability to transform normal cells into cancerous cells.
Answer:
Retrovirus

4. The separated bands of DNA are cut out from the agarose gel and extracted from gel piece. This step is known as …………………………………. .
Answer:
Elution.

5. Restriction enzymes belong to a larger class of enzymes called ……………………… .
Answer:
Nucleases.

6. Inactive Bt toxin is converted into an active form due to the ……………………… pH of the insect’s gut.
Answer:
Alkaline.

7. Cells in continuous culture system are maintained in ………………………… phase of growth.
Answer:
Log / Exponential

8. Golden rice is a genetically modified crop enriched with ………………………………….. .
Answer:
Vitamin A

9. The inherent capacity of a plant cell to produce a whole plant is known as ………………………. .
Answer:
Totipotency.

III. One Word Answer Questions

Question 1.
After 10 PCR cycles, how many DNA molecules are formed from one DNA molecule?
Answer:
1024

Question 2.
In plants, which enzyme is used to dissolve cell wall during DNA isolation?
Answer:
Cellulase

Question 3.
Agarose is a natural polymer and is extracted from? ,
Answer:
Seaweeds

Question 4.
What do you call a group of letters that form the same word when read in both forward and backward directions?
Answer:
Palindromic sequence

Question 5.
Which enzyme is commonly used-to join DNA fragments?
Answer:
DNA ligase

Question 6.
Name the plasmid extracted from Agrobacterium and used to deliver the gene of interest into a variety of dicot plants?
Answer:
Ti Plasmid

Question 7.
Which sequence is responsible for controlling the copy number of the linked DNA?
Answer:
Origin of Replication (Ori)

Question 8.
Any part of the plant used to culture in vitro to obtain plantlets is known as?
Answer:
Explant

Question 9.
What do you call the plants that are genetically identical to the original plant from which they were grown?
Answer:
Somaclones

Objective Questions

Question 1.
Restriction enzymes are commonly referred to as
1. Antibiotics
2. Chromosomes
3. Restriction enzymes
4. Genes
Answer:
3. Restriction enzymes

Question 2.
The carrier used to introduce foreign DNA into a host organism is
1. r-DNA
2. Messenger RNA
3. Plasmid
4. Chromosome
Answer:
3. Plasmid

Question 3.
Which enzymes cut DNA strands at specific recognition sites?
1. Ligases
2. Exonucleases
3. Endonucleases
4. Polymerases
Answer:
2. Exonucleases

Question 4.
A palindromic sequence in DNA
1. Serves as the recognition site for restriction enzymes
2. Functions as a plasmid
3. Acts as a vector
4. Represents the origin of replication
Answer:
1. Serves as the recognition site for restriction enzymes

Question 5.
Polymerase Chain Reaction (PCR) is mainly employed for
1. DNA precipitation
2. Gene amplification
3. Cutting DNA with restriction enzymes
4. Isolation of a desired gene
Answer:
2. Gene amplification

Question 6.
In the naming of restriction enzymes, the first letter denotes
1. Species
2. Order of isolation
3. Name of the strain
4. Genus
Answer:
4. Genus

Question 7.
Which of the following represents recombinant (chimeric) DNA?
1. Plasmid DNA
2. rDNA
3. Gene of interest after cutting
4. Primer
Answer:
2. rDNA

Question 8.
Which technique is extensively used in DNA fingerprinting?
1. Restriction digestion
2. Isolation of desired genes
3. Gene amplification
4. Extraction of DNA from agarose gel
Answer:
3. Gene amplification

Question 9.
Introduction of a DNA fragment into a bacterial host cell is known as
1. Translation
2. Transformation
3. Transcription
4. Transduction
Answer:
2. Transformation

Question 10.
DNA fragments stained after electrophoresis appear as
1. Fine crystal clusters
2. Thread-like structures
3. Bright violet bands
4. Bright orange bands
Answer:
4. Bright orange bands

Question 11.
The initial step in recombinant DNA technology is
1. Insertion of gene into vector
2. Selection of transformed cells
3. Isolation of the desired gene
4. Ligation of gene with vector
Answer:
3. Isolation of the desired gene

Question 12.
The major enzyme involved in DNA replication in E. coli is
1. DNA-dependent DNA polymerase
2. Restriction endonuclease
3. Ligase
4. DNA-dependent RNA polymerase
Answer:
1. DNA-dependent DNA polymerase

Question 13.
The chief enzyme responsible for PCR is
1. DNA ligase
2. Restriction enzyme
3. Taq polymerase
4. Hydrolase
Answer:
3. Taq polymerase

Question 14.
A commonly used vector for producing transgenic organisms is
1. Ti plasmid
2. Cos sites
3. pBR322
4. Coliphage lambda
Answer:
1. Ti plasmid

Question 15.
pUC101 belongs to the category of
1. Virus
2. Mutagen
3. Plasmid
4. Cosmid
Answer:
3. Plasmid

Question 16.
The first recombinant DNA molecule was constructed using the plasmid of
1. E. coli
2. Bacillus thuringiensis
3. Yeast
4. Salmonella typhimurium
Answer:
4. Salmonella typhimurium

Question 17.
Which among the following are known as molecular scissors?
1. Hind III
2. Bam I
3. EcoRI
4. All of these
Answer:
4. All of these

Question 18.
A labelled nucleic acid fragment used to detect a specific gene is called
1. DNA probe
2. Plasmid DNA
3. T-DNA
4. cDNA
Answer:
1. DNA probe

Question 19.
The enzyme that cuts host DNA during the restriction-modification system in E. coli is
1. Restriction exonuclease
2. Plasmid
3. Restriction endonuclease
4. Type III restriction enzyme
Answer:
3. Restriction endonuclease

Question 20.
EcoRI digestion produces the sticky end sequence
1. AATTC
2. TTAA
3. GAATTC
4. CTTAA
Answer:
2. TTAA

Question 21.
Which gene transfer method is most suitable for animal cells?
1. Gene gun method
2. Calcium-mediated uptake
3. Microinjection
4. Electroporation
Answer:
3. Microinjection

Question 22.
The ‘rop’ gene present in plasmids is associated with
1. Cloning site
2. Replication site
3. Selectable marker
4. Proteins involved in replication
Answer:
4. Proteins involved in replication

Question 23.
A nucleic acid probe tagged with a radioactive molecule can be
1. Double-stranded DNA only
2. Single-stranded RNA only
3. Single-stranded DNA only
4. Both single-stranded DNA and RNA
Answer:
4. Both single-stranded DNA and RNA

Question 24.
Which of the following is NOT required for PCR?
1. DNA template
2. Helicase enzyme
3. Oligonucleotide primer
4. Taq polymerase
Answer:
2. Helicase enzyme

Question 25.
The matrix most commonly employed in gel electrophoresis is
1. Ethidium bromide
2. Sulphite bromide
3. Agarose
4. Sulphate bromide
Answer:
3. Agarose

Question 26.
Which of the following can serve as the recognition site for EcoRI?
1. AATCT
2. GAATTC
3. ATCATC
4. ATGCAT
Answer:
2. GAATTC

Question 27.
After six PCR cycles, the number of DNA molecules produced is
1. 64
2. 16
3. 4
4. 32
Answer:
1. 64

Question 28.
If foreign DNA is inserted into the Sail site of pBR322, transformants can grow on
1. Ampicillin
2. Both antibiotics
3. Tetracycline
4. None
Answer:
1. Ampicillin

Question 29.
Which vector is commonly used to transfer genes into animal cells?
1. Ti plasmid
2.E. coli
3. Retroviruses
4. Disarmed retroviruses
Answer:
4. Disarmed retroviruses

Question 30.
The ratio of triple hydrogen-bonded to double hydrogen-bonded base pairs in an EcoRI recognition site is
1. 2: 1
2. 1: 2
3. 3: 2
4. 3: 4
Answer:
2. 1: 2

Question 31.
The Ti plasmid used for developing transgenic plants is obtained from
1. Rhizobium
2. Yeast plasmid
3. Agrobacterium
4. Azotobacter
Answer:
3. Agrobacterium

Question 32.
Identify the incorrectly matched pair
1. Restriction endonuclease – PstI
2. Retroviruses – T-DNA
3. Recognition sequence of EcoRI – 5′ GAATTC 3′
4. Plasmid – Ringlet of DNA
Answer:
2. Retroviruses – T-DNA

Question 33.
The thermostable DNA polymerase used in PCR is isolated from
1. Beggiatoa
2. Thiobacillus
3. Thermus aquaticus
4. Thermobacter
Answer:
3. Thermus aquaticus

Question 34.
Gene amplification using primers is carried out by
1. ELISA
2. Polymerase Chain Reaction
3. Gene gun
4. Microinjection
Answer:
2. Polymerase Chain Reaction

Question 35.
An antibiotic resistance gene in a vector is mainly used for selecting
1. Recombinant cells
2. Transformed cells
3. Competent cells
4. None of these
Answer:
2. Transformed cells

Question 36.
Gene-specific probes are employed in
1. Colony isolation
2. Colony identification
3. Colony hybridization
4. Colony hybridization
Answer:
3. Colony hybridization

Question 37.
DNA fragments generated by the same restriction enzyme can be joined together using
1. DNA polymerase
2. Restriction enzyme
3. DNA ligase
4. E. coli
Answer:
3. DNA ligase

Question 38.
If nitrogen bases are randomly distributed, the minimum number of nucleotides required for the sequence GAATTC to appear once is
1. 256
2. 512
3. 1024
4. 4096
Answer:
2. 512

Question 39.
The most essential feature of a plasmid is
1. Selectable marker
2. Restriction sites
3. Origin of replication (ori)
4. All of these
Answer:
3. Origin of replication (ori)

Question 40.
In genetic engineering, antibiotics are mainly used as
1. Selectable markers
2. Sources of replication
3. Culture-protecting agents
4. Healthy vector selectors
Answer:
1. Selectable markers

Question 41.
PCR primarily functions in
1. Translation
2. DNA amplification
3. Transduction
4. None of these
Answer:
2. DNA amplification

Question 42.
While cutting DNA, molecular scissors cleave
1. Phosphodiester bonds only
2. Hydrogen bonds only
3. Both phosphodiester and hydrogen bonds
4. Hydrogen and peptide bonds
Answer:
3. Both phosphodiester and hydrogen bonds

43. Agarose gel is
1. A natural polymer obtained from seaweeds
2. A natural polymer from fungi
3. A synthetic polymer from red algae
4. An artificial polymer
Answer:
1. A natural polymer obtained from seaweeds

Question 44.
Which primers are used to initiate PCR?
1. RNA primers
2. DNA primers
3. Both DNA and RNA primers
4. None of these
Answer:
1. RNA primers

Question 45.
The ori sequence in a plasmid refers to
1. The site from which replication begins
2. A sequence controlling copy number
3. A restriction site
4. Both (1) and (2)
Answer:
4. Both (1) and (2)

Reviewing AP Inter 2nd Year Botany Study Material Chapter 4 Microbes in Human Welfare Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Botany 4th Lesson Microbes in Human Welfare Questions and Answers

IV. Very Short Answer Questions

Question 1.
Why does Swiss cheese have big holes? Name the bacteria responsible for it.
Answer:

1. The large holes seen in Swiss cheese are formed due to the release of significant amounts of carbon dioxide (CO₂) during fermentation.
2. The bacterium Propionibacterium sharmanii is responsible for producing these holes.

Question 2.
What are fermentors?(AP MAY-17, 22)
Answer:
Fermentors are large-scale containers used for the commercial production of beverages, antibiotics, and other microbial products.

Question 3.
Name any two industrially important enzymes. (AP Mar-19)(AP Mar-17,19, 22)
Answer:
Examples of industrially important enzymes are: Amylase, Lipase, Streptokinase.

Question 4.
What are Baculoviruses?
Answer:

1. Baculoviruses are viruses that specifically infect insects and other arthropods.
2. They are widely used as biological control agents, and most belong to the genus Nucleopolyhedrovirus.

Question 5.
Which group of bacteria is found in both the rumen of cattle and sludge of sewage treatment plants?
Answer:
Methanogens.

Question 6.
Name the scientists who were credited with showing the role of penicillin as an antibiotic.
Answer:

1. Alexander Fleming discovered penicillin.
2. Ernst Chain and Howard Florey demonstrated and established its effectiveness as an antibiotic.

Question 7.
Name any one species of fungi used in the production of antibiotics.
Answer:

1. A fungus commonly used in antibiotic production is Penicillium notatum.
2. It is the source of the antibiotic Penicillin.

Question 8.
What is sewage? In what way can sewage be harmful to us?
Answer:
Sewage refers to municipal wastewater, which contains human excreta, organic matter, and numerous microorganisms.

1. Many of these microorganisms may be disease-causing pathogens. Therefore, sewage should not be discharged directly into rivers, lakes, or other natural water bodies without treatment.
2. Before disposal, it is treated in sewage treatment plants (STPs) using naturally occurring heterotrophic microbes.
3. If untreated sewage contaminates drinking water sources, it can spread diseases and create health problems in humans and domestic animals.

Question 9.
What is the key difference between primary and secondary sewage treatment?
Answer:

1. Primary Sewage Treatment: It is a physical process that removes suspended particles through methods such as filtration and sedimentation. It is relatively simple and less costly.
2. Secondary Sewage Treatment: It is a biological process in which the primary effluent is transferred to aeration tanks where microorganisms degrade organic matter. This method is comparatively more complex, time-consuming, and expensive.

Question 10.
How do biofertilizers enrich the fertility of the soil?
Answer:
Biofertilizers improve soil fertility through the action of living organisms such as bacteria, fungi, and cyanobacteria that enhance soil nutrient availability.

They increase soil fertility through the following processes :

1. Nitrogen fixation
2. Phosphate solubilization
3. Addition of organic matter to the soil.

V. Short Answer Questions

Question 1.
Why are floes important in the biological treatment of waste water?
Answer:
Floes are clusters of aerobic bacteria associated with fungal filaments, forming mesh-like aggregates.
Role of floes in biological treatment:

1. The primary effluent is transferred into large aeration tanks, where air is continuously supplied, and the contents are mechanically agitated.
2. These conditions promote the rapid multiplication of beneficial aerobic microorganisms, resulting in the formation of flocs.
3. While growing, these microbes break down a major portion of the organic matter present in the effluent and thereby reduce its Biochemical Oxygen Demand (BOD).
4. The treated effluent is then sent to a settling tank where the bacterial flocs settle down.
5. This settled material is known as activated sludge.
6. A small portion of the activated sludge is recycled back into the aeration tank to serve as inoculum, while the remaining sludge is transferred to anaerobic sludge digesters.

Question 2.
Name the bacterium responsible for the conversion of milk into curd. Mention two benefits of curd formation.
Answer:
The bacterium responsible for converting milk into curd is Lactobacillus, a member of the group known as Lactic Acid Bacteria (LAB).

Two advantages of curd formation are:

1. Improved Nutritional Value: The process enhances the nutritional quality of milk by increasing the amount of Vitamin B₁₂.
2. Protection Against Harmful Microbes: LAB helps maintain a healthy gut environment by suppressing the growth of disease-causing microorganisms in the digestive system.

Question 3.
What is BOD? Why is it an important parameter in sewage treatment?
Answer:
BOD (Biochemical Oxygen Demand) is the quantity of oxygen required by microorganisms to decompose the organic matter present in one litre of water.

Importance in sewage treatment:

• Measure of Organic Pollution: BOD reflects the amount of biodegradable organic matter present in water.
• Indicator of Water Quality: A higher BOD value indicates greater pollution and a larger amount of organic waste.
• Useful in Biological Treatment: During secondary treatment, aerobic microbes consume organic matter and help reduce BOD.
• Assessment of Treatment Efficiency: A decrease in BOD indicates successful sewage treatment and improved water quality.

Question 4.
Define methanogens. Give one example and their role in biogas production.
Answer:
Methanogens are anaerobic microorganisms that grow on cellulosic substrates and produce methane gas along with carbon dioxide and hydrogen in the absence of oxygen. Example: Methanobacterium Role in biogas production:

• Methanogens function in anaerobic sludge digesters and decompose organic matter.
• They help break down cellulose-rich material and release biogas.
• These organisms are also present in the rumen of cattle, where they assist in cellulose digestion.
• The methane-rich biogas produced is combustible and serves as a valuable fuel for cooking and lighting.

Question 5.
Write two advantages of mycorrhizal association of plants.
Answer:
Mycorrhiza is a mutually beneficial association between the roots of higher plants and certain fungi, commonly belonging to the genus Glomus. In this association, both the plant and the fungus benefit from each other.

Advantages of mycorrhizal association :

1. Improved Nutrient Absorption: The fungal hyphae spread extensively in the soil and increase the surface area for absorption. They help the plant absorb essential minerals, especially phosphorus, from the soil and transfer them to the plant roots, thereby enhancing plant growth.
2. Increased Resistance and Better Growth: Plants associated with mycorrhiza show greater resistance to root-borne pathogens and improved tolerance to drought and salinity. As a result, the plants grow healthier and exhibit better overall development.

Question 6.
What is meant by biocontrol? Give one example of microbial biocontrol agent.
Answer:
Biocontrol refers to the use of living organisms or biological methods to manage plant diseases and’pests instead of relying on chemical pesticides.
Example of a microbial biocontrol agent: Bacillus thuringiensis (Bt)

1. It is a bacterial biocontrol agent used against butterfly caterpillars.
2. It is available as dried spores that are mixed with water and sprayed on crops.
3. When insect larvae feed on the treated plants, the toxin becomes active in their gut and kills them.
4. It specifically targets caterpillars without affecting beneficial insects

VI. Long Answer Questions

Question 1.
Describe the role of microbes in the production of household products with suitable examples.
Answer:
Microorganisms are essential components of the biosphere and occur along with plants and animals. They include bacteria, fungi, protozoa, viruses, and other microscopic forms of life. Many microbes are beneficial and are widely used in the preparation of household products through fermentation.

Important characteristics of microbes:

1. Wide Distribution: Microorganisms are found everywhere-in soil, water, air, and inside the bodies of plants and animals. They can survive even in extreme habitats such as hot springs, deep oceans, frozen regions, and highly acidic environments.
2. Microscopic Nature: Most microbes are microscopic and cannot be seen with the naked eye. However, some bacteria and fungi can be grown on nutrient media to form visible colonies for study.
3. Importance to Human Life: Although some microbes cause diseases, many are useful and play an important role in producing several everyday products.
4. Dairy Products (Curd): Microorganisms such as Lactobacillus and other Lactic Acid Bacteria (LAB) convert milk into curd. During this process, LAB produce acids that coagulate milk proteins and partially digest them. A small quantity of curd acts as a starter culture and multiplies rapidly under suitable conditions. This process also enhances the nutritional value of milk by increasing Vitamin B12 content.
5. Fermented Dough (Dosa, Idli and Bread): The batter used for preparing foods such as dosa and idli undergoes fermentation by microbes. The soft and fluffy texture develops because of the release of carbon dioxide (CO₂) gas. Similarly, bread making involves the use of baker’s yeast (Saccharomyces cerevisiae).
6. Traditional Fermented Foods and Drinks: A traditional beverage called Toddy is prepared by fermenting palm sap. Microorganisms are also used in fermenting fish, soybean, and bamboo shoots to prepare different food products.
7. Cheese Production: Microbes contribute to the manufacture of different varieties of cheese by providing characteristic texture, flavour and aroma. The holes in Swiss cheese are formed due to CO₂ produced by Propionibacterium sharmanii. Roquefort cheese develops its special flavour through the action of selected fungi.

Question 2.
Explain the steps involved in secondary sewage treatment and the role of microbes in the process.
Answer:
Secondary sewage treatment, also called biological treatment, utilizes naturally occurring microorganisms to remove organic pollutants from wastewater. Unlike primary treatment, which is mainly physical, this stage depends on microbial activity.

The process involves the following steps:
1. Aeration and Aerobic Digestion:
Process: The primary effluent is transferred into large aeration tanks where it is continuously stirred and supplied with air.
Role of Microbes: Aeration promotes the growth of aerobic microorganisms that form floes, which are aggregates of bacteria associated with fungal filaments.
Reduction of BOD: As these microbes consume organic matter, the Biochemical Oxygen Demand (BOD) of the wastewater decreases considerably.

2. Sedimentation and Activated Sludge:
Process: After BOD is reduced, the effluent is moved into a settling tank.
Role of Microbes: The microbial flocs settle at the bottom and form activated sludge. Inoculum: A small amount of activated sludge is recycled back into the aeration tank to initiate treatment of the next batch.

3. Anaerobic Sludge Digestion:
Process: The remaining activated sludge is transferred into anaerobic sludge digesters.
Role of Microbes: Anaerobic bacteria digest the bacterial and fungal biomass present in the sludge.
Biogas Formation: During digestion, gases such as methane, hydrogen sulphide and carbon dioxide are produced, collectively forming biogas.

4. Final Disposal:

• After the biological treatment is complete, the treated effluent is generally considered safe enough to be released into natural water bodies like rivers and streams.
• This microbial methodology has been the primary way of treating millions of gallons of wastewater worldwide for over a century, as no man-made technology has yet rivaled its efficiency. Thus, Secondary sewage treatment relies on microbes to remove organic pollutants, reduce BOD, and produce useful by-products like biogas, making wastewater safe for disposal.

Question 3.
Discuss the industrial applications of microbes in the production of fermented beverages, antibiotics, and bioactive molecules.
Answer:
Microorganisms are extensively employed in industries for producing fermented beverages, antibiotics, and various bioactive compounds. These products are manufactured in large fermenters under controlled environmental conditions.
1. Fermented Beverages: Yeasts are commonly used to prepare alcoholic beverages such as wine, beer, whisky, brandy and rum.

• Microbe Used: The most widely used yeast is Saccharomyces cerevisiae (brewer’s yeast).
• Process: It ferments malted cereals and fruit juices to produce ethanol.
• Products: Wine and beer are obtained without distillation, whereas whisky, brandy and rum are produced after distillation of the fermented broth.

2. Antibiotics:

• Antibiotics are microbial substances that suppress or destroy disease- causing organisms.
• Penicillin was the first antibiotic discovered by Alexander Fleming from the fungus Penicillium notatum.
• The therapeutic value of penicillin was later demonstrated by Ernst Chain and Howard Florey.
• Antibiotics have greatly reduced deaths caused by diseases such as plague, diphtheria, whooping cough, and leprosy.

3. Bioactive Molecules and Chemicals: Microorganisms are used to manufacture several organic acids, enzymes, and bioactive compounds:

Organic Acids: Examples :

• Citric acid – Aspergillus niger
• Acetic acid – Acetobacter aceti
• Butyric acid – Clostridium butylicum
• Lactic acid – Lactobacillus

Industrial Enzymes:

• Lipases – used in detergents for removing oily stains.
• Pectinases and Proteases – used in clarifying bottled fruit juices.
• Streptokinase – produced by Streptococcus and used as a ‘clot-buster’.

Bioactive Molecules:

• Cyclosporin A, produced by Trichoderma polysporum, is used as an immunosuppressant during organ transplantation.
• Statins, produced by Monascus purpureus, help lower blood cholesterol levels by inhibiting the enzyme responsible for cholesterol synthesis.

Question 4.
Explain the process of biogas production in a typical biogas plant and name the main microbes involved.
Answer:
Biogas is a gaseous fuel mainly consisting of methane (CH₄), carbon dioxide (CO₂), traces of hydrogen sulphide (H₂S), and moisture. It is generated by the anaerobic decomposition of cattle dung, domestic waste, and agricultural residues by microorganisms.

a) Biogas Production from Sludge:

1. A small amount of activated sludge is recycled back into the aeration tank as inoculum.
2. In anaerobic digesters, methanogenic bacteria digest the bacterial and fungal biomass present in the sludge.
3. During digestion, gases such as methane, carbon dioxide, and hydrogen sulphide are released, forming biogas.

b) Biogas Production from Dung:

1. A biogas plant contains a deep concrete tank in which dung slurry is collected.
2. A floating cover is placed over the slurry and rises as gas accumulates.
3. The plant has an outlet connected to pipelines for supplying biogas to nearby houses.
4. The spent slurry is removed through a separate outlet and is used as an organic fertilizer.

Main Microbes Involved: Methanogens (e.g., Methanobacterium) are the primary microorganisms responsible for biogas production.

I. Multiple Choice Questions

Question 1.
Which microbe is commonly used to convert milk into curd?
1. Acetobacter
2. Rhizobium
3. Lactobacillus
4. Clostridium
Answer:
3. Lactobacillus

Question 2.
Penicillin was discovered by :
1. Robert Koch
2. Edward Jenner
3. Louis Pasteur
4. Alexander Fleming
Answer:
4. Alexander Fleming

Question 3.
Which enzyme is used to remove blood clots in heart patients?
1. Lipase
2. Amylase
3. Streptokinase
4. Cellulase
Answer:
3. Streptokinase

Question 4.
The bacterium that produces butyric acid is:
1. Clostridium
2. Acetobacter
3. Lactobacillus
4. Azotobacter
Answer:
1. Clostridium

Question 5.
Swiss cheese holes are due to release of CO₂ produced by :
1. Propionibacterium sharmanii
2. Saccharomyces cerevisiae
3. Lactobacillus
4. Penicillium
Answer:
1. Propionibacterium sharmanii

Question 6.
Methanogens are found in :
1. Aerobic soil
2. Vinegar
3. Cold water bodies
4. Rumen of cattle
Answer:
4. Rumen of cattle

Question 7.
The fungus used to produce cyclosporin A is:
1. Penicillium notatum
2. Trichoderma polysporum
3. Aspergillus niger
4. Saccharomyces
Answer:
2. Trichoderma polysporum

Question 8.
Which of the following microbes helps in nitrogen fixation in paddy fields?
1. Acetobacter
2. Penicillium
3. Glomus
4. Nostoc
Answer:
4. Nostoc

Question 9.
The ‘clot buster’ enzyme is produced by:
1. Streptomyces
2. Streptococcus
3. Bacillus
4. Pseudomonas
Answer:
2. Streptococcus

Question 10.
Which gas is predominantly present in biogas?
1. Carbon dioxide
2. Nitrogen
3. Oxygen
4. Methane
Answer:
4. Methane

II. Fill in the Blanks

1. The microbe used for the commercial production of ethanol is ………………………. .
Answer:
Saccharomyces cerevisiae

2. The puffed-up appearance of dough is due to the production of ………………………… .
Answer:
CO₂

3. …………………………… beverages are produced without distillation.
Answer:
Wine & Beer

4. ……………………….. antibiotic was extensively used to treat American soldiers wounded in the World War II.
Answer:
Penicillin.

5. …………………………… is used in the production of Swiss cheese.
Answer:
Propionibacterium sharmanii

6. During biological treatment, microbes significantly reduce ………………………. by consuming organic matter in effluent.
Answer:
Biochemical Oxygen Demand (BOD)

7. ………………………………. is an immunosuppressive drug obtained from Trichoderma polysporum.
Answer:
Cyclosporin A

8. …………………………….. are the enzymes helpful in removing oily stains from the laundry.
Answer:
Lipases

9. ………………….. is a free-living fungus which is an effective biocontrol agent of several plant pathogens.
Answer:
Trichoderma

10. ……………………….. is an example of a methanogen.
Answer:
Methanobacterium

III. One Word Answer Questions

Question 1.
Which bacterium is responsible for the production of acetic acid?
Answer:
Acetobacter aceti

Question 2.
Name the enzyme commonly used as a ‘clot buster’ in heart attack patients.
Answer:
Streptokinase

Question 3.
Which fungus is known for producing Cyclosporin A?
Answer:
Trichoderma polysporum

Question 4.
Name the yeast that is commercially used for producing statins.
Answer:
Monascuspurpureus

Question 5.
What is the full form of BOD?
Answer:
Biochemical Oxygen Demand

Question 6.
Mention one methanogenic bacterium present in the rumen of cattle.
Answer:
Methanobacterium

Question 7.
Which bacterium acts as a biocontrol agent against butterfly caterpillars?
Answer:
Bacillus thuringiensis

Question 8.
Name a fungal genus that forms mycorrhizal associations.
Answer:
Glomus.

Question 9.
Which group of viruses is used as a biological control agent for insect pests?
Answer:
Nucleopolyhedroviruses

Question 10.
Name the traditional Indian beverage prepared by fermenting palm sap.
Answer:
Toddy

Objective Questions

Question 1.
Which bacterium is widely used in converting milk into curd?
1. Bacillus
2. Thiobacillus
3. Lactobacillus
4. Ferrobacillus
Answer:
3. Lactobacillus

Question 2.
LAB (Lactic Acid Bacteria) enhances the nutritional value of curd by increasing the amount of:
1. Vitamin B₁₂
2. Vitamin B₁
3. Vitamin B₂
4. Vitamin B₆
Answer:
1. Vitamin B₁₂

Question 3.
Bread dough fermentation is mainly carried out by:
1. Candida utilis
2. Lactobacillus
3. Saccharomyces cerevisiae
4. Candida lipolytica
Answer:
3. Saccharomyces cerevisiae

Question 4.
The batter used for preparing Idli and Dosa undergoes fermentation by:
1. Bacteria
2. Algae
3. Protozoans
4. Viruses
Answer:
1. Bacteria

Question 5.
Cheese and yoghurt are obtained through the process of:
1. Pasteurisation
2. Fermentation
3. Distillation
4. Dehydration
Answer:
2. Fermentation

Question 6.
Which acid is commonly formed during microbial fermentation?
1. Oxaloacetic acid
2. Lactic acid
3. Fumaric acid
4. Acetic acid
Answer:
2. Lactic acid

Question 7.
Who discovered Penicillin?
1. Louis Pasteur
2. Waksman
3. Alexander Fleming
4. Edward Jenner
Answer:
3. Alexander Fleming

Question 8.
Which one of the following is NOT a beverage?
1. Beer
2. Rum
3. Penicillin
4. Wine
Answer:
3. Penicillin

Question 9.
Large-scale vessels used for culturing microbes are called:
1. Sterilizers
2. Fermenters
3. Autoclaves
4. Stabilizers
Answer:
2. Fermenters

Question 10.
Which was the first antibiotic discovered?
1. Aureomycin
2. Penicillin
3. Ampicillin
4. Tetracycline
Answer:
2. Penicillin

Question 11.
Citric acid is commercially produced by:
1. Yeasts
2. Aspergillus niger
3. Penicillium notatum
4. Chaetomium cellulolyticum
Answer:
2. Aspergillus niger

Question 12.
The first artificially synthesized hormone was:
1. Inulin
2. Casein
3. Insulin
4. Collagen
Answer:
3. Insulin

Question 13.
Beer is commonly prepared from:
1. Grapes
2. Molasses
3. Barley
4. Rye
Answer:
3. Barley

Question 14.
Penicillin is obtained from:
1. Fungus
2. Virus
3. Bacterium
4. Algae
Answer:
1. Fungus

Question 15.
Select the incorrect statement regarding antibiotics:
1. Antibiotics are effective only against specific microbes
2. The first antibiotic discovered was penicillin
3. Some individuals may develop allergy to antibiotics
4. An antibiotic can cure any disease
Answer:
1. Antibiotics are effective only against specific microbes

Question 16.
Ethanol production from starch is carried out using:
1. Lactobacillus
2. Azotobacter
3. Acetobacter
4. Saccharomyces
Answer:
4. Saccharomyces

Question 17.
A vaccine is:
1. A treated bacterial, viral, or protein preparation
2. A treated phage
3. A treated alga
4. A treated fungus
Answer:
1. A treated bacterial, viral, or protein preparation

Question 18.
The term “antibiotic” was introduced by:
1. Edward Jenner
2. Waksman
3. Dr. Y. Subba Rao
4. Alexander Fleming
Answer:
2. Waksman

Question 19.
After a viral infection, infected host cells release:
1. Antibody
2. Interferon
3. Antigen
4. Interleukin
Answer:
2. Interferon

Question 20.
What is the scientific name of baker’s yeast?
1. Candida utilis
2. Saccharomyces cerevisiae
3. Candida lipolytica
4. Chaetomium cellulolyticum
Answer:
2. Saccharomyces cerevisiae

Question 21.
Statins are commercially used as:
1. Blood cholesterol-lowering agents
2. Immunosuppressive agents
3. Clot busters
4. Oil-stain removers
Answer:
1. Blood cholesterol-lowering agents

Question 22.
Which enzyme is commonly used to remove oily stains?
1. Pectinase
2. Lipase
3. Urease
4. Sucrase
Answer:
2. Lipase

Question 23.
BOD stands for:
1. Biological Oxygen Demand
2. Biogeographical Oxygen Demand
3. Biochemical Oxygen Demand
4. Biophysical Oxygen Demand
Answer:
3. Biochemical Oxygen Demand

Question 24.
The major constituent of biogas is:
1. Acetone
2. Methane
3. Ethane
4. Ammonia
Answer:
2. Methane

Question 25.
The microorganisms mainly involved in gobar gas plants are:
1. Denitrifying bacteria
2. Nitrogen-fixing bacteria
3. Methanogens
4. Nitrifying bacteria
Answer:
3. Methanogens

Question 26.
Sewage purification is carried out by:
1. Antibiotics
2. Microbes
3. Fertilizers
4. Antiseptics
Answer:
2. Microbes

Question 27.
Baculoviruses specifically infect:
1. Arthropods
2. Coelenterates
3. Annelids
4. Nematodes
Answer:
1. Arthropods

Question 28.
Which of the following is a symbiotic nitrogen-fixing bacterium?
1. Azotobacter
2. Rhizobium
3. Clostridium
4. Azospirillum
Answer:
2. Rhizobium

Question 29.
Which among the following acts as a biofertilizer?
1. Rhizobium and legume association
2. Blue-green algae and Azolla
3. Nostoc and grasses
4. E. coli and legume association
Answer:
2. Blue-green algae and Azolla

Question 30.
Farmers can enhance paddy yield by nearly 50% through the use of:
1. Rhizobium
2. Farmyard manure
3. Cyanobacteria
4. Cyanobacteria and Azolla
Answer:
4. Cyanobacteria and Azolla

Reviewing AP Inter 2nd Year Botany Study Material Chapter 3 Molecular Basis of Inheritance Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Botany 3rd Lesson Molecular Basis of Inheritance Questions and Answers

IV. Very Short Answer Questions

Question 1.
Distinguish between heterochromatin and euchromatin. Which of the two is transcriptionally active?
Answer:

Question 2.
Who proved that DNA is genetic material? On which organism they worked?
Answer:

1. Alfred Hershey and Martha Chase demonstrated that DNA is the genetic material.
2. They conducted their experiment using bacteriophages, which are viruses that infect bacteria.

Question 3.
What is the function of DNA polymerase?
Answer:

1. DNA polymerase is a highly efficient enzyme that catalyses the polymerisation of a large number of nucleotides within a very short period.
2. It also carries out the polymerisation process with a high level of accuracy.

Question 4.
What are the components of a nucleotide?
Answer:
A nucleotide consists of 3 components, nitrogen base, pentose sugar and phosphate group.

Question 5.
Given below is the sequence of coding strand of DNA in a transcription unit. 5′-AATGACGCCTATTAGG-3 ′. Write the sequence of
a) Its complementary strand
b) The mRNA
Answer:
a) 3 ‘TTACTGCGGATAATCC’ 5
b) 5 ‘AAUGACGCCUAUUAGG’ 3

Question 6.
Name any two viruses which have RNA as genetic material.
Answer:

1. Influenza virus
2. Polio virus
3. HIV

Question 7.
What are the components of a transcriptional unit?
Answer:
The components of transcription unit are Promoter, structural gene, and terminator.

• A promoter,
• the structural gene, and
• A Terminator.

Question 8.
What is the difference between exons and introns?
Answer:

1. Exons: These are the coding regions of a gene. They are retained in the mature (processed) RNA after RNA processing.
2. Introns: These are the non-coding regions of a gene. They are removed during RNA processing and are absent in the mature (processed) RNA.

Question 9.
What is meant by capping and tailing?
Answer:

1. Capping: The addition of a modified nucleotide, methylguanosine triphosphate (mwG), to the 52 end of hnRNA is known as capping.
2. Tailing: The addition of 200 – 300 adenylate (poly-A) residues to the 32 end of hnRNA is called tailing.

Question 10.
What is meant by point mutation? Give an example.
Answer:

1. A point mutation is a mutation that occurs due to a change in a single base pair of a DNA molecule.
2. Example: Sickle cell anaemia.

Question 11.
What is meant by charging of tRNA?
Answer:
Charging of tRNA is the process in which an amino acid is activated in the presence of ATP and then attached to its corresponding (cognate) tRNA.

Question 12.
What is the function of the codon AUG? (AP MAY-22) (AP-20)
Answer:
AUG performs two important functions:

1. It serves as the start (initiation) codon during protein synthesis.
2. It specifies the amino acid methionine.

Question 13.
What do you understand ‘Stop codon’, and mention them. (AP MAR-15,19)
Answer:

1. Stop codons are codons that signal the termination of protein synthesis.
2. The three stop codons are UAA, UAG, and UGA.
3. These codons do not specify any amino acid.

Question 14.
What is the difference between the template strand and a coding strand in a DNA molecule?
Answer:

1. During transcription, the two strands of the DNA molecule separate from each other.
2. The template strand serves as the complementary strand that guides the synthesis of mRNA.

The coding strand has the same nucleotide sequence as the mRNA (except that thymine is replaced by uracil in RNA) and does not directly serve as the template for transcription.

Question 15.
Write any two chemical differences between DNA and RNA.
Answer:

Question 16.
In a typical DNA molecule, the proportion of Thymine is 30%. Find out the percentage
Answer:

• Adenme =30%,
• Guanine = 20%,
• Cytosine = 20% (Total 70%).

Question 17.
The proportion of nucleotides in a given nucleic acid are: Adenine 18%, Guanine 30%, Cytosine 42%, and Uracil 10%. Name the nucleic acid and mention the number of strands in it.
Answer:

1. It is RNA (presence of uracil)
2. It is only single-stranded.

V. Short Answer Questions

Question 1.
Define transformation. Give a brief account of Griffith’s experiment,
Answer:

1. Transformation: Transformation is the process in which a cell undergoes a genetic change by taking up and incorporating genetic material from its surroundings through the cell membrane.
2. In 1928, Frederick Griffith performed a series of experiments on the bacterium Streptococcus pneumoniae, which causes pneumonia.
3. During his study, he observed that the bacteria could change from one form to another when grown in a culture medium.

4. He identified two strains of the bacterium:

• Smooth strain (S-type) – forms smooth colonies due to the presence of a capsule.
• Rough strain (R-type) – lacks a capsule and forms rough colonies.

5. The S-type bacteria were disease-causing (virulent), whereas the R-type bacteria were harmless (non-virulent).
6. When living S-type cells were injected into mice, the mice developed pneumonia and died.
7. When living R-type cells were injected into mice, the mice remained healthy and survived.
8. Injection of heat-killed S-type cells did not cause disease in mice.
9. However, when heat-killed S-type cells were mixed with living R-type cells and injected into mice, the mice died, and living S-type bacteria were recovered from them
10. Griffith concluded that the living R-type bacteria had been converted into S-type bacteria by some substance released from the dead S-type cells.
11. He called this substance the transforming principle, which was later identified as DNA.

Question 2.
Discuss the significance of heavy isotope of nitrogen in Meselson and Stahl’s experiment?
Answer:
In 1958, Meselson and Stahl used the heavy nitrogen isotope 15N to demonstrate that DNA replication follows a semi-conservative mode.
1. Importance of ¹⁵N:

• Labelling DNA: E. coli bacteria were grown in a medium containing ¹⁵NH₄Cl, allowing ¹⁵N to become incorporated into DNA, producing heavy DNA.
• Density Difference: Since ¹⁵N is heavier than ¹⁴N, DNA containing ¹⁵N could be easily distinguished from normal DNA based on density.
• Separation by Centrifugation: DNA samples were separated using CsCl density gradient centrifugation.
  Heavy DNA (¹⁵N) formed a lower band.
  Light DNA (¹⁴N) formed an upper band.

2. Tracking DNA Replication:
When bacteria were shifted to a medium containing ¹⁴N:
After one generation: Only hybrid DNA (intermediate density) was observed.
After two generations: Both hybrid DNA and light DNA were present in equal proportions. Proof of

Semi-Conservative Replication:
These observations proved that every newly formed DNA molecule contains:

1. One parental strand (old strand) (¹⁵N)
2. One newly synthesized strand (new strand) (¹⁴N). Thus, the use of ¹⁵N enabled scientists to trace DNA replication and provided the first experimental evidence for the semi-conservative replication of DNA.

Question 3.
How does t-RNA act as an adaptor molecule?
Answer:
t-RNA (transfer RNA), also known as soluble RNA (s-RNA), functions as an adaptor molecule because it connects the genetic information present in mRNA with the amino acids required for protein synthesis. This concept was proposed by Francis Crick.

How t-RNA Functions as an Adapter:
1. Two Functional Ends: t-RNA possesses two important binding regions:

• Anticodon loop – recognizes and binds to the complementary codon on mRNA.
• Amino acid acceptor end – attaches to a specific amino acid.

This enables t-RNA to link codons with their corresponding amino acids.

2. Specificity: Each type of t-RNA carries only a particular amino acid, ensuring accuracy during protein synthesis.
3. Charging (Aminoacylation): Before translation begins, amino acids are attached to their respective t-RNAs using ATP. This process is called charging of t-RNA or aminoacylation.
4. Structure: t-RNA has a cloverleaf-shaped secondary structure, while its three-dimensional structure resembles an inverted L-shape, which helps it function efficiently.

During Translation:

• The anticodon of t-RNA pairs with the codon on mRNA and delivers the correct amino acid to the ribosome.
• Thus, t-RNA serves as a bridge between mRNA codons and amino acids, ensuring proper synthesis of proteins.

Question 4.
How many types of RNA polymerases exist in eukaryotic cells? Write their names and functions.
Answer:
Eukaryotic cells contain three major RNA polymerases in the nucleus (apart from those present in organelles). They are:

1. RNA Polymerase I: Responsible for the synthesis of rRNA molecules (28S, 18S, and 5.8S rRNA).
2. RNA Polymerase II: Synthesizes hnRNA (heterogeneous nuclear RNA), the precursor of messenger RNA (mRNA).
3. RNA Polymerase III: Carries out the transcription of tRNA, 5S rRNA, and snRNA (small nuclear RNA).

Question 5.
Identify the A, B, C, and D in the given picture.

Answer:

• A → Transcription Unit (Structural Gene): The DNA segment located between the initiation and termination signals where transcription takes place.
• B → Promoter: The DNA region where RNA polymerase binds to initiate transcription.
• C → Coding Strand (Non-template Strand): The DNA strand whose sequence is similar to the RNA transcript, except that thymine (T) is replaced by uracil (U) in RNA.
• D → Terminator: The DNA sequence that signals the end of transcription.

Question 6.
Draw the schematic representation of Lac operon.
Answer:

Question 7.
What are the differences between DNA and RNA?
Answer:

Question 8.
Write the salient features of Genetic code? (AP Mar. 16,17, 24)
Answer:
The important characteristics of the genetic code:

1. The genetic code is a collection of instructions that guides the conversion of genetic information into proteins containing 20 amino acids.
2. It is made up of 64 nucleotide triplets, and each triplet is known as a codon.
3. Out of the 64 codons, 61 codons specify amino acids, while 3 codons do not code for any amino acid and function as stop codons.
4. Each codon specifies only one particular amino acid, making the genetic code unambiguous and specific.
5. Some amino acids are represented by more than one codon; therefore, the genetic code is said to be degenerate.
6. Codons are read continuously on mRNA without any gaps or punctuation marks, making the code comma-less.
7. The genetic code is nearly universal, meaning it functions similarly in almost all living organisms.
8. Example: The codon UUU codes for Phenylalanine (Phe) in organisms ranging from bacteria to humans.

Question 9.
Give a brief account on nucleosome with a neat labelled diagram.
Answer:

1. A nucleosome is the fundamental bead-like structural unit of chromatin.
2. It consists of a histone octamer (eight histone protein molecules) around which DNA is wrapped, along with a DNA segment of about 200 base pairs.
3. The negatively charged DNA strand coils around the positively charged histone octamer to form a nucleosome.
4. Nucleosomes help in packing and compacting DNA within the nucleus.
5. Chromatin is composed of DNA and basic histone proteins.
6. Nucleosomes are arranged repeatedly along the chromatin fibre, forming its basic repeating units.
7. Under an electron microscope, chromatin appears as a “beads-on-a-string” structure due to the presence of nucleosomes.

VI. Long Answer Questions

Question 1.
Give an account of post-transcriptional modifications of a eukaryotic mRNA.
Answer:
The primary transcript (hnRNA) undergoes several modifications after transcription inside the nucleus before becoming mature mRNA.

5′ Capping:

• The first modification is the addition of a 7-methylguanosine cap at the 5′ end of hnRNA through an unusual 5′ – 5′ triphosphate linkage.
• Extra methyl groups may also be added to the cap structure.
• The cap protects mRNA from degradation, helps in its stability, and assists in the initiation of translation.

2. Addition of Poly-A Tail:

• A long chain of about 40-200 adenine nucleotides is added to the 3′ end of mRNA.
• This structure is called the Poly-A tail.
• It is added after transcription and is not directly coded by DNA.
• The Poly-A tail improves mRNA stability and helps in its transport from the nucleus to the cytoplasm.
• As mRNA ages in the cytoplasm, the Poly-A tail gradually becomes shorter.

3. Splicing (Removal of Introns):

• Eukaryotic hnRNA contains both coding and non-coding sequences.
• The non-coding regions called introns are removed.
• The coding regions called exons are joined together to form mature mRNA.
• After these modifications, the mature mRNA leaves the nucleus and participates in protein synthesis.

Question 2.
Discuss the process of translation in detail.
Answer:
Translation is the process by which amino acids are linked together according to the sequence of codons in mRNA to form a polypeptide chain. The process occurs in three stages:

1. Initiation:

• Amino acids are first attached to their specific tRNAs using ATP (charging of tRNA).
• The start codon AUG on mRNA is recognized by the charged initiator tRNA.
• The ribosome acts as the site where translation occurs.
• It contains two binding sites for tRNA molecules.
• The small ribosomal subunit binds to mRNA at the start codon, followed by the attachment of the large subunit.

2. Elongation:

• The ribosome moves along the mRNA one codon at a time.
• Each incoming amino acid carried by tRNA is joined to the growing polypeptide chain by a peptide bond.
• This step continues repeatedly, resulting in the elongation of the protein chain.

3. Termination:

• Translation stops when the ribosome reaches a stop codon (UAA, UAG, or UGA).
• The completed polypeptide is released, and the ribosomal subunits detach from the mRNA.

Question 3.
Give the salient features of the Double helix structure of DNA.
Answer:
The Double Helix Model of DNA was proposed by Watson and Crick
1. DNA consists of two polynucleotide strands. Each strand has a sugar-phosphate backbone on the outside and nitrogenous bases projecting inward.
2. The two strands run in opposite directions (anti-parallel). If one strand runs 5′ → 3′, the other runs 3′ → 5′.
3. The nitrogenous bases pair through hydrogen bonds:

• Adenine (A) pairs with Thymine (T) by two hydrogen bonds.
• Guanine (G) pairs with Cytosine
• by three hydrogen bonds. This complementary pairing maintains a constant diameter of about 20 Å throughout the helix.

4. DNA is a right-handed helix. One complete turn measures 3.4 nm and contains about 10 base pairs. The distance between two adjacent base pairs is 0.34 nm.
5. The base pairs are stacked one above another, which provides additional stability to the DNA molecule along with hydrogen bonding.

Question 4.
Describe the Lac operon with schematic representation.
Answer:

1. The Lac operon is a group of regulatory and structural genes that function together to control the metabolism of lactose in bacteria.
2. It consists of important regions such as the regulator gene (i), promoter (P), operator (O), and three structural genes: Z, Y, and A.
3. The operon enables the utilization of lactose by converting it into simpler sugars like glucose and galactose.
4. In the Lac operon, lactose acts as an inducer.
5. When lactose is present, it binds to the repressor protein and makes it inactive. RNA polymerase can then bind to the promoter and begin transcription.
6. As a result, the structural genes Z, Y, and A are expressed and produce their respective enzymes.
7. These enzymes help in the breakdown and utilization of lactose. When lactose levels decrease, the repressor protein is produced again.
8. The active repressor binds to the operator region and blocks RNA polymerase from transcribing the operon. Therefore, transcription stops in the absence of the inducer.

Schematic representation of the Lac operon

I. Multiple Choice Questions

Question 1.
Which among the following is not true?
1. Bacteriophage Φ × 174 has 5386 nucleotides.
2. Bacteriophage lambda has 48502 bp.
3. Escherichiacolihas 4.6 × 10⁶ bp.
4. Haploid content of human DNA is 6.6 × 10⁹ bp.
Answer:
4. Haploid content of human DNA is 6.6 × 10⁹ bp.

Question 2.
As per the Watson and Crick DNA model, the pitch length of the DNA double helix is
1. 0.34 nm
2. 3.4 nm
3. 3.4 Å
4. 0.34 Å
Answer:
2. 3.4 nm

Question 3.
Which of the following nitrogen base is absent in RNA?
1. Adenine
2. Cytosine
3. Uracil
4. Thymine
Answer:
4. Thymine

Question 4.
Approximate length of a typical mammalian cell DNA is
1. 2.6 meters
2. 2 meters
3. 2.2 metres
4. 2.4 meters
Answer:
3. 2.2 metres

Question 5.
A molecule should not have one of the following features to act as a genetic material
1. It should be able to generate its replica (Replication).
2. It should be stable chemically and structurally.
3. It should provide the scope for rapid changes that are required for evolution.
4. It should be able to express itself in the form of‘Mendelian Characters’.
Answer:
3. It should provide the scope for rapid changes that are required for evolution.

Question 6.
DNA fragments can be joined by the following enzyme.
1. DNA polymerase
2. DNA Ligase
3. DNase
4. DNA-dependent RNA polymerase
Answer:
2. DNA Ligase

Question 7.
During the transcription RNA Polymerase binds to the following region of transcriptional unit.
1. Terminator
2. Structural gene
3. Promoter
4. Operator
Answer:
3. Promoter

Question 8.
What is the role of RNA polymerase III in the process of transcription in Eukaryotes?
1. Transcription of tRNA, 5 s rRNA, and snRNA
2. Transcription of precursor of mRNA
3. Transcription of only snRNAs
4. Transcription of rRNAs(28S, 18S and 5.8S)
Answer:
1. Transcription of tRNA, 5 s rRNA, and snRNA

Question 9.
‘Operon’concept was proposed by
1. Meselson and Stahl
2. Watson and Crick
3. Jacob and Monod
4. Har Gobind Khorana
Answer:
3. Jacob and Monod

Question 10.
Enzyme permease is synthesized by
1. z-gene
2. a-gene
3. i-gene
4. y-gene
Answer:
4. y-gene

II. Fill in the Blanks

1. DNA is a polymer of ………………………………….. .
Answer:
Deoxyribonucleotides.

2. Cytosine, Uracil …………………………. and are together called Pyrimidines.
Answer:
Thymine.

3. DNA was first identified by Friedrich Miescher, and he named it as ………………………….. .
Answer:
Nuclein

4. James Watson and Francis Crick …………………………… proposed model of DNA.
Answer:
Double Helix

5. Discontinuous synthesis of DNA takes place on ……………………………. parental strand of DNA.
Answer:
5’→ 3′

6. ……………………………… is loosely packed and transcriptionally active chromatin.
Answer:
Euchromatin

7. The average rate of polymerisation by DNA polymerase enzyme in E.coli is approximately …………………. per second.
Answer:
2000 bp

8. In bacterial cells, with the help of ………………………….. factor, RNA polymerase initiates transcription.
Answer:
Sigma or σ

9. During transcription, ……………………… enzyme plays a key role in DNA helix unwinding.
Answer:
RNA polymerase

10. Copying of genetic information from one strand of the DNA into RNA is termed as …………………. .
Answer:
transcription

III. One Word Answer Questions

Question 1.
Name the pyrimidine which is common in both DNA and RNA.
Answer:
Cytosine

Question 2.
Which feature of DNA molecule enables the constant distance between two strands?
Answer:
Purine and pyrimidine base pairing.

Question 3.
Who proposed central dogma in molecular biology?
Answer:
Francis Crick.

Question 4.
Write the names of basic amino acids which are rich in histone proteins.
Answer:
Lysine and arginine

Question 5.
At what specific region, DNA replication initiates?
Answer:
‘Ori’region

Question 6.
Name the bacteria which is used by Griffith for conducting transformation experiments.
Answer:
Streptococcus pneumoniae

Question 7.
Normal E. coli was allowed to grow in a medium containing ¹⁵NH₄Cl for 80 minutes; then what would be the proportions of light, hybrid, and heavy density DNA molecules?
Answer:
0: 2: 14

Question 8.
In which direction does the DNA polymerase enzyme polymerises the DNA.
Answer:
5′ → 3′

Question 9.
Write the name of Severo Ochoa enzyme.
Answer:
Polynucleotide phosphorylase

Question 10.
Who first proposed that the‘codon’is a triplet?
Answer:
George Gamow

Objective Questions

Question 1.
The basic building blocks of nucleic acids are known as
1. Nitrogen bases
2. Nucleotides
3. Pentose monosaccharides
4. Nucleosides
Answer:
2. Nucleotides

Question 2.
The genetic molecule found most abundantly in living organisms is
1. RNA
2. tRNA
3. DNA
4. mRNA
Answer:
3. DNA

Question 3.
The repeating units that make up nucleic acid chains are called
1. Nucleosides
2. Heterocyclic molecules
3. Nucleotides
4. Pentose sugars
Answer:
3. Nucleotides

Question 4.
The principal genetic material in most organisms is
1. mRNA
2. DNA
3. rRNA
4. RNA
Answer:
3. rRNA

Question 5.
DNA molecule carries a
1. Positive charge
2. No charge
3. Negative charge
4. Positive charge only during denaturation
Answer:
3. Negative charge

Question 6.
Another name for thymine is
1. Thymidylic acid
2. 5-methyluracil
3. Uridine
4. Thymidine
Answer:
2. 5-methyluracil

Question 7.
DNA acts as a template for the synthesis of
1. DNA only
2. Proteins only
3. Both DNA and RNA
4. RNA only
Answer:
3. Both DNA and RNA

Question 8.
DNA replication generally takes place during
1. Interphase
2. Meiosis
3. Mitosis
4. Interkinesis
Answer:
1. Interphase

Question 9.
RNA differs from DNA in the
1. Type of pyrimidines
2. Number of polynucleotide strands
3. Type of purines
4. Type of sugar
Answer:
3. Type of purines

Question 10.
In DNA, each sugar molecule is attached to
1. One phosphate and two nitrogen bases
2. Two phosphates and two nitrogen bases
3. Two phosphates and one nitrogen base
4. One nitrogen base and one phosphate
Answer:
3. Two phosphates and one nitrogen base

Question 11.
DNA is absent in
1. Mitochondria
2. Plasmids
3. Chloroplasts
4. Ribosomes
Answer:
4. Ribosomes

Question 14.
Which statement correctly describes a property of DNA?
1. It should evolve rapidly
2. It should be biochemically unstable
3. It should mutate very quickly
4. It should be able to replicate
Answer:
4. It should be able to replicate

Question 15.
In eukaryotes, one mRNA molecule is generally produced from
1. Three structural genes
2. A single structural gene
3. Many structural genes
4. Two structural genes
Answer:
2. A single structural gene

Question 16.
The approximate time required for DNA replication in E. coli is
1. 20 minutes
2. 40 minutes
3. 18 minutes
4. 80 minutes
Answer:
3. 18 minutes

Question 17.
The total length of DNA present in a typical human cell is about
1. 4.2 metres
2. 3.2 metres
3. 1.2 metres
4. 2 metres
Answer:
4. 2 metres

Question 18.
DNA strands are described as antiparallel because of
1. Peptide bonds
2. Hydrogen bonds
3. Phosphodiester bonds
4. Disulphide bonds
Answer:
2. Hydrogen bonds

Question 19.
One complete turn of B-form DNA measures nearly
1. 2.0 nm
2. 20 nm
3. 3.4 nm
4. 0.34 nm
Answer:
3. 3.4 nm

Question 20.
The transfer of genetic information from DNA into RNA is called
1. Polyadenylation
2. Transformation
3. Transcription
4. Translation
Answer:
3. Transcription

Question 21.
During transcription, the DNA strand that is copied is called
1. Coding strand
2. Terminator strand
3. Template strand
4. Promoter strand
Answer:
1. Coding strand

Question 22.
The DNA strand not directly used in RNA synthesis is known as
1. Template strand
2. Coding strand
3. Antisense strand
4. Complementary strand
Answer:
2. Coding strand

Question 23.
In bacteria, transcription and translation occur respectively in
1. Cytoplasm and cytoplasm
2. Nucleus and cytoplasm
3. Cytoplasm and genephore
4. Nucleoid and nucleus
Answer:
1. Cytoplasm and cytoplasm

Question 24.
Identify the incorrect match.
1. mRNA-template for protein synthesis
2. tRNA-reader of genetic code
3. rRNA – catalytic role in translation
4. Transcription – DNA-dependent DNA polymerase
Answer:
4. Transcription – DNA-dependent DNA polymerase

Question 25.
The primary transcript is longer than functional hnRNA in
1. Prokaryotic animals
2. Cyanobacteria
3. Eukaryotes
4. Prokaryotes
Answer:
3. Eukaryotes

Question 26.
Transcription of snRNA is carried out by
1. RNA polymerase II
2. RNA polymerase III
3. RNA polymerase I
4. RNA polymerase I & II
Answer:
2. RNA polymerase III

Question 27.
Introns are commonly found in
1. Eukaryotes only
2. Both prokaryotes and eukaryotes
3. Bacteria only
4. Prokaryotes only
Answer:
1. Eukaryotes only

Question 28.
Exons are present in
1. Only in prokaryotes
2. Only in eukaryotic plants
3. Both prokaryotes and eukaryotes
4. Only in eukaryotes
Answer:
4. Only in eukaryotes

Question 29.
Split genes are characteristic of
1. Cyanobacteria
2. Bacteria
3. All Monerans
4. Eukaryotes
Answer:
4. Eukaryotes

Question 30.
Genes are primarily made up of
1. Glycoproteins
2. Histone proteins
3. Polynucleotides
4. Lipoproteins
Answer:
3. Polynucleotides

Question 31.
The synthesis of repressor mRNA is controlled by
1. ‘i’ gene
2. ‘Y’ gene
3. ‘Z’ gene
4. ‘O’ gene
Answer:
1. ‘i’ gene

Question 32.
The total number of nucleotides present in bacteriophage lambda DNA is
1. 97040
2. 48520
3. 48502
4. 97004
Answer:
3. 48502

Question 33.
The transcriptionally active form of chromatin is called
1. Heterochromatin
2. Euchromatin
3. Chromatogram
4. Prochromatin
Answer:
2. Euchromatin

Question 34.
DNA is composed of which of the following?
A) Sugar
B) Phosphate
C) Purines
D) Pyrimidines
1. A, B and C only
2. A and C only
3. A, B, C and D
4. A and D only
Answer:
3. A, B, C and D

Question 35.
A nucleoside differs from a nucleotide by
1. Presence of phosphate group
2. Absence of phosphate group
3. Absence of sugar
4. Absence of nitrogen base
Answer:
2. Absence of phosphate group

Question 36.
The earliest proof that DNA acts as the genetic material came from
1. Phage infection
2. Bacterial transformation
3. Bacterial translocation
4. Transfection
Answer:
1. Phage infection

Question 37.
Griffith conducted his transformation experiment using
1. Streptococcus pyogenes
2. Escherichia coli
3. Streptococcus pneumoniae
4. Streptomyces griseus
Answer:
3. Streptococcus pneumoniae

Question 38.
Avery, MacLeod, and McCarty identified …………………….. as the transforming principle.
1. Proteins
2. Polysaccharides
3. DNA
4. RNA
Answer:
3. DNA

Question 39.
Around each histone core, DNA wraps approximately
1. Two turns
2. Five turns
3. Three turns
4. Four turns
Answer:
1. Two turns

Question 40.
Uracil differs from thymine because it
1. Has a methyl group
2. Has two C-N rings
3. Contains an NH₂ group
4. Lacks a methyl group
Answer:
4. Lacks a methyl group

Question 41.
The haploid DNA content in humans is approximately
1. 48502 bp
2. 5386 nucleotides
3. 3.3 × 10⁹ bp
4. 4.6 × 10⁶ bp
Answer:
3. 3.3 × 10⁹ bp

Question 42.
A nucleotide is composed of
1. Sugar + Phosphate
2. Base + Sugar
3. Base + Phosphate
4. Base + Sugar + Phosphate
Answer:
2. Base + Sugar

Question 43.
Which of the following is NOT a property of genetic material?
1. Self-replication
2. Chemical and structural stability
3. Fast mutation
4. Self-expression
Answer:
3. Fast mutation

Question 44.
Which statement is NOT a characteristic of RNA?
1. RNA evolves slowly
2. RNA is unstable and degradable
3. RNA can act as a catalyst
4. RNA mutates faster than DNA
Answer:
1. RNA evolves slowly

Question 45.
In the Hershey and Chase experiment, radioactive 35 S labelled
1. Cytosol of bacteria
2. Phage DNA
3. Protein coat of bacteriophage
4. Bacterial DNA
Answer:
3. Protein coat of bacteriophage

Question 46.
A cluster of closely associated structural and regulatory genes functioning together is called
1. Genetic code
2. Operon
3. Monocistronic gene
4. Regulon
Answer:
2. Operon

Question 47.
Heterogeneous nuclear RNA (hnRNA) is converted into mRNA through
1. Splicing only
2. Capping only
3. Tailing only
4. All of the above
Answer:
4. All of the above

Question 48.
The number of sense codons coding for amino acids is
1. 60
2. 64
3. 61
4. 32
Answer:
3. 61

Question 49.
Identify the correct statement.
1. ACG codes for Asparagine
2. UGU codes for Tyrosine
3. CGA codes for Serine
4. GUA codes for Valine
Answer:
4. GUA codes for Valine

Question 50.
Which of the following is NOT a feature of the genetic code?
1. It is degenerate
2. It is nearly universal
3. It is non-continuous
4. It is unambiguous
Answer:
3. It is non-continuous

Question 51.
The functional unit of a gene is known as
1. Muton
2. Cistron
3. Intron
4. Recon
Answer:
2. Cistron

Question 52.
Mature (processed) mRNA contains
1. Exons only
2. Introns only
3. Exons and introns
4. Capping at 3′ end
Answer:
1. Exons only

Question 53.
The RNA molecule that performs both structural and catalytic functions during translation is
1. tRNA
2. rRNA
3. sRNA
4. mRNA
Answer:
2. rRNA

Question 54.
Ochoa’s enzyme refers to
1. DNA polymerase
2. Polynucleotide phosphorylase
3. Peptidyl transferase
4. DNA ligase
Answer:
3. Peptidyl transferase

Question 55.
The gene responsible for producing the repressor protein is
1. Promoter gene
2. Structural gene
3. Regulator gene
4. Operator gene
Answer:
3. Regulator gene

Question 56.
The attachment site for the repressor protein produced by the regulator gene is the
1. Structural gene
2. Promoter region
3. Operator gene
4. Inducer
Answer:
3. Operator gene

Question 57.
The rule stating that in DNA the amount of adenine equals thymine and guanine equals cytosine is called
1. Jordan’s rule
2. Chargaff’s rule
3. Aflen’s rule
4. Stahl’s rule
Answer:
2. Chargaff’s rule

Question 58.
Purines are chemically classified as
1. Monocycic
2. Dicyclic and heterocyclic
3. Homocycic
4. Dicyclic and homocyclic
Answer:
2. Dicyclic and heterocyclic

Question 59.
A phosphate group is attached to the 5′-OH of a nucleotide through
1. Glycosidic linkage
2. Hydrogen linkage
3. Phosphoester linkage
4. Both (1) & (2)
Answer:
3. Phosphoester linkage

Question 60.
In the Lac operon, the inducer combines with
1. Promoter gene
2. Repressor protein
3. Repressor gene
4. Operator gene
Answer:
2. Repressor protein

Reviewing AP Inter 2nd Year Botany Study Material Chapter 2 Principles of Inheritance and Variation Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Botany 2nd Lesson Principles of Inheritance and Variation Questions and Answers

IV. Very Short Answer Questions

Question 1.
What is the cross between the F₁ progeny and a homozygous recessive parent called? How is it useful?
Answer:

1. Such a cross is known as a Test Cross.
2. It is used to identify the genotype of the organism being tested.

Question 2.
Do you think Mendel’s laws of inheritance would have been different if the characters he chosen were located on the same chromosome?
Answer:
Yes. If the genes for different characters were present on the same chromosome, they would tend to be inherited together and would not follow Mendel’s Law of Independent Assortment

Question 3.
Who proposed the chromosome theory of inheritance? [AP MAR-17,19]
Answer:
Sutton and Boveri.

Question 4.
Define true breeding and mention its significance.
Answer:

1. True Breeding: Continuous self-pollination over generations, resulting in offspring with the same traits, is called true breeding.
2. Significance: It ensures the stable inheritance and expression of traits through many generations.

Question 5.
Explain the terms phenotype and genotype. [AP MAR-16,23,24]
Answer:

• The observable physical appearance of an organism is called its Phenotype.
• The genetic constitution of an organism is called its Genotype.

Question 6.
What is linkage?
Answer:
Linkage is the tendency of genes located on the same chromosome to remain associated and get inherited together.

Question 7.
What will be the phenotypic ratio in the offspring obtained from the following crosses?
a) AA x aa
b) Aa x Aa
Note: Gene A is dominant over gene a.
Answer:
a) 1: 1
b) 3: 1.

Question 8.
In garden peas, the gene T for tall is dominant over its allele for dwarf. Give the genotypes of the parents in the following crosses.
a) Tall × Dwarf producing all tall plants.
b) Tall × dwarf producing half tall and half dwarf.
Answer:
(a) Tall x Dwarf → All tall plants: To obtain all tall offspring, the tall parent must be homozygous dominant (TT) and the dwarf parent must be homozygous recessive (tt). Genotypes: TT × tt
(b) Tall × Dwarf → Half tall and half dwarf (1:1 ratio): This ratio is obtained when the tall parent is heterozygous (Tt) and the dwarf parent is tt. Genotypes: Tt x tt

V. Short Answer Questions

Question 1.
Differentiate between the following
A) Dominant and Recessive B) Homozygous and Heterozygous
Answer:
A)

B)

Question 2.
Explain the law of dominance using a monohybrid cross.
Answer:
Monohybrid Cross:

1. A cross involving two individuals differing in one pair of contrasting characters is called a monohybrid cross.
2. In his experiments, Mendel crossed tall and dwarf pea plants to study the inheritance of a single trait. Based on these observations, he proposed the Law of Dominance.

Law of Dominance:

1. Characters are controlled by discrete hereditary units called factors.
2. Factors occur in pairs.
3. When two contrasting factors are present together, one factor (dominant) expresses itself, while the other (recessive) remains hidden.
4. This law explains why only one parental trait appears in the F₁ generation and why both traits reappear in the F₂ generation. It also explains the 3:1 phenotypic ratio obtained in F₂.

Question 3.
Define and describe a test cross. [AP MAR-25,16]
Answer:

1. A test cross is the crossing of an F₁ individual with a recessive parent.
2. It is used to determine whether an individual is homozygous or heterozygous.
3. A monohybrid test cross produces a 1:1 phenotypic ratio.
4. A dihybrid test cross produces a ratio.

Question 4.
Explain incomplete dominance with examples.
Answer:
Incomplete Dominance:

1. Incomplete dominance is a condition in which neither allele is completely dominant nor completely recessive.
2. A common example is the inheritance of flower colour in Snapdragon (Antirrhinum).
3. When a red-flowered plant (RR) is crossed with a white-flowered plant (rr), all F₁ plants (Rr) show pink flowers.
4. When the F₁ plants are self-pollinated, the F₂ generation shows: 1 (RR) Red, 2 (Rr) Pink, 1 (rr) White.
5. The genotypic ratio remains 1:2:1, similar to Mendel’s monohybrid cross.
6. However, the phenotypic ratio also becomes 1:2:1 because neither allele completely dominates the other.
7. Thus, in incomplete dominance, both phenotypic and genotypic ratios in the F₂ generation are 1:2:1.

Question 5.
Define the law of segregation and the law of independent assortment.
Answer:
a) Law of Segregation:

1. The two alleles of a gene remain separate and do not blend when present together in a heterozygous condition.
2. During meiosis, these alleles separate so that each gamete receives only one allele.
3. This law is based on the results of monohybrid crosses.
4. It was proposed by Mendel.
5. It is also called the Law of Purity of Gametes.

b) Law of Independent Assortment:

1. When two or more pairs of contrasting traits are considered, the inheritance of one pair of factors is independent of the other pair.
2. This law is based on the results of dihybrid crosses.
3. It was proposed by Mendel as his Second Law.

Question 6.
Why did T.H. Morgan select fruit flies for his genetical experiments?
Answer:
Thomas Hunt Morgan selected the fruit fly, Drosophila melanogaster, for genetic studies because of several advantages:

• Easy Cultivation: They can be easily reared on a simple synthetic medium under laboratory conditions.
• Short Life Cycle: Their life cycle is completed in about two weeks, allowing the study of many generations in a short time.
• High Reproductive Capacity: A single mating produces a large number of offspring, providing sufficient data for genetic analysis.
• Distinct Sexual Dimorphism: Male and female flies can be easily distinguished, making breeding experiments convenient.
• Visible Genetic Variations: They exhibit many hereditary variations that can be observed easily under low-power microscopes.

VI. Long Answer Questions

Question 1.
Explain the dihybrid cross with the help of Punnett square.
Answer:
A dihybrid cross is a genetic cross involving two parents that differ in two pairs of contrasting characters. Mendel used this cross to study the inheritance of two traits at the same time and concluded that different pairs of traits assort independently.
1. The Parental (P) Generation: Mendel crossed a pea plant with round, yellow seeds and a pea plant with wrinkled, green seeds.

• Genotypes: Round, yellow parent – RRYY; wrinkled, green parent = rryy
• Dominance: Yellow seed colour (Y) is dominant over green (y). Round seed shape (R) is dominant over wrinkled (r).
• Gamete: RRYY parent produces RY gametes; rryy parent produces ry gametes.

2. The F Generation: After fertilization, the offspring produced have the genotype.  RrYy Phenotype: All F plants are round and yellow because dominant alleles mask the recessive alleles.

3. Gamete Formation and Independent Assortment: When F plants are self-pollinated, they produce four kinds of gametes. According to the Law of Independent Assortment, segregation of R and r occurs independently of Y and y. The four types of gametes are: RY, Ry, rY, ry. Each type is formed in equal proportion (25% or 1/4).

4. The F Punnett Square: A Punnett square is a diagram used to predict all possible combinations of offspring. For a dihybrid cross, a 16-square Punnett grid is used because four types of male gametes combine with four types of female gametes.

Punnett Square (F, Generation)

5. Results of the Cross: Analysis of the sixteen combinations in the F₁ generation gives: Phenotypic Ratio: 9 : 3 : 3: 1

• 9 Round, Yellow (Parental type)
• 3 Round, Green (Recombinant)
• 3 Wrinkled, Yellow (Recombinant)
• 1 Wrinkled, Green (Parental type)

Genotypic Ratio: 1 : 2 : 1: 2 : 4 : 2 : 1 : 2 : 1
Conclusion: Law of Independent Assortment: Based on the results of the dihybrid cross, Mendel proposed the Law of Independent Assortment, which states that: “When two pairs of traits are inherited together, the segregation of one pair of factors is independent of the segregation of the other pair”. This means that inheritance of one trait (such as seed shape) does not influence the inheritance of another trait (such as seed colour).

Question 2.
Write notes on chromosomal theory of inheritance?
Answer:
The Chromosomal Theory of Inheritance was proposed by Walter Sutton and Theodor Boveri. According to this theory, genes are located on chromosomes, and chromosomes are responsible for transmitting hereditary characters from parents to offspring.

1. Main Principles:

• Genes are arranged in a linear sequence on chromosomes.
• Chromosomes occur in homologous pairs in diploid organisms, with one chromosome of each pair inherited from each parent.
• During meiosis, homologous chromosomes separate, causing alleles to segregate. This provides an explanation for Mendel’s Law of Segregation.
• Different chromosome pairs assort independently during meiosis. This explains Mendel’s Law of Independent Assortment.
• During fertilization, male and female gametes fuse, restoring the diploid chromosome number in the zygote.

2. Observations of Sutton and Boveri :
They observed that chromosomes:

• Occur in pairs during meiosis.
• Separate and move into different gametes. This behaviour closely resembles that of Mendel’s hereditary factors (genes). Therefore, they concluded that chromosomes carry genes and control inheritance.

3. Experimental Evidence: The theory was later supported by Thomas Hunt Morgan through his experiments on Drosophila melanogaster. He discovered:

• Linkage: Genes present on the same chromosome tend to be inherited together.
• This demonstrated that all genes do not assort independently.

4. Extension of the Theory:

• Not all genes follow independent assortment.
• Genes present on the same chromosome exhibit linkage.
• Crossing over during meiosis produces recombination.

5. Significance:

• Provides the physical (cytological) basis of inheritance.
• Establishes a connection between cytology and genetics.
• Provides scientific support for Mendel’s laws.
• Helps in understanding genetic variation and evolution.

Conclusion: The chromosomal theory states that genes are located on chromosomes, and their inheritance follows chromosome behaviour during meiosis and fertilization, thereby explaining how traits are transmitted from parents to offspring.

Question 3.
Explain the following
a) Law of dominance
b) Incomplete dominance
Answer:
Monohybrid Cross:

1. A cross between two individuals differing in one contrasting character is called a monohybrid cross.
2. In his hybridization experiments, Mendel crossed tall and dwarf pea plants to study the inheritance of a single gene. From these observations, he proposed the Law of Dominance.

a) Law of Dominance:

1. Characters are controlled bý discrete hereditary units called factors.
2. Factors occur in pairs.
3. When two contrasting factors are present together, one factor (dominant) expresses itself while the other (recessive) remains hidden.
4. The law explains why only one parental character appears in the F generation and why both parental characters reappear in the F₁ generation. It also explains the 3:1 phenotypic ratio observed in F₂.

b) Incomplete dominance

1. Incomplete dominance is a phenomenon in which neither allele is completely dominant nor completely recessive.
2. Example: Flower colour inheritance in Snapdragon (Antirrhinum).
3. When a homozygous red-flowered plant (RR) is crossed with a homozygous white-flowered plant (rr), all F₁ plants (Rr) show pink flowers.
4. On self-pollination of F₁ plants, the F₂ generation shows:

1(RR) Red
2(Rr) Pink
1(rr) White

5. The genotypic ratio remains the same as Mendel’s monohybrid cross (1: 2: 1).
6. However, due to incomplete dominance, the phenotypic ratio also becomes 1: 2: 1 instead of 3: 1.
Therefore, in incomplete dominance, both the phenotypic ratio and genotypic ratio in the F₂ generation are 1:2:1.

I. Multiple Choice Questions

Question 1.
The tendency of offsprings to resemble their parents is called
1. Variation
2. Mutation
3. Inheritance
4. Recombination
Answer:
3. Inheritance

Question 2.
The condition of dissimilar allelic pair of a gene is known as
1. homozygous
2. heterozygous
3. linkage
4. polyallelic
Answer:
2. heterozygous

Question 3.
The proportion of plants that were tall and dwarf in F₂-generation of Mendel experiment, respectively.
1. 1/4th and 3/4th
2. 3/4th and 1/4th
3. 2/3rdand 1/3rd
4. 1/3rd and 4/3rd
Answer:
2. 3/4th and 1/4th

Question 4.
When alleles of two contrasting traits are present together, one of the traits expresses itself during the cross while the other remains hidden. This phenomenon is known as
1. Law of purity of gametes
2. Law of segregation
3. Law of dominance
4. Law of independent assortment
Answer:
3. Law of dominance

Question 5.
What is the genotype of the wrinkled phenotype of pea seeds?
1. rr
2. Rr
3. RR
4. Wr
Answer:
1. rr

Question 6.
Find out the phenotype of A, B, C, D from the given cross in Snapdragon (R = red and r= white).

1. A-Red, B-Pink, C-Pink, D-White
2. A-Red, B-Red, C-White, D-White
3. A-Pink, B-Red, C-White, D-White
4. A-Pink, B-Red, C-Red, D-White
Answer:
1. A-Red, B-Pink, C-Pink, D-White

Question 7.
How many phenotypes and genotypes are possible in ABO blood group systems
1. Four, five
2. Four, six
3. Four, seven
4. Three, four
Answer:
2. Four, six

Question 8.
Starch synthesis gene in pea plant is an example of
1. single gene produces more than one effect
2. multiple genes produce more than one effect
3. two genes produce more than one effect
4. multiple genes produce less than one effect
Answer:
1. single gene produces more than one effect

Question 9.
Match the following columns.

A B C D
1) 2 4 3 1
2) 2 4 1 4
3) 3 4 1 2
4) 1 4 1 3
Answer:
1) 2 4 3 1

Question 10.
The types of gametes formed by the genotype RrYy are
1. RY, Ry, rY, ry
2. RY, Ry, ry, ry
3. Ry, Ry, Yy, ry
4. Rr, RR, Yy, YY
Answer:
1. RY, Ry, rY, ry

Question 11.
What is the genotypic ratio in Mendel dihybrid cross?
1. 1 : 2 : 2 : 4 : 1 : 2 : 1 : 2 :1
2. 1 : 4 : 1 : 1 : 2 : 1 : 1 : 2 : 1
3. 1 : 4 : 2 : 1 : 1 :1 : 2 : 1
4. 4 : 2 : 1 : 1 : 1 : 1 : 2 : 1 : 1
Answer:
1. 1 : 2 : 2 : 4 : 1 : 2 : 1 : 2 :1

Question 12.
Strength of the linkage between the two genes is
1. proportionate to the distance between them
2. inversely proportionate to the distance between them
3. depending on length of the chromosomes
4. depending on size of the chromosomes
Answer:
2. inversely proportionate to the distance between them

II. Fill in the Blanks

1. The cross between parents, which differ in two pairs of contrasting characters, is ………………….. .
Answer:
Dihybrid cross

2. Mendel selected …………………………. true-breeding pea plant varieties, as pairs which were similar except for one character with contrasting traits.
Answer:
14

3. The production of gametes by the parents, the formation of the zygotes, the F₁ and F₂ plants can be understood from a diagram is called ………………………… .
Answer:
Punnett Square or Checkerboard.

4. The inheritance of flower colour in ……………….. is a good example to understand incomplete dominance.
Answer:
Dog flower (snapdragon or Antirrhinum)

5. The first genetic map of a chromosome was constructed by ……………………….. .
Answer:
Alfred Sturtevant.

6. The phenotypic ratio of Snapdragon plant monohybrid cross in F₂ generation is ………………….. .
Answer:
1: 2: 1

7. The crossing of F₁ with its recessive parent is called ……………………….. .
Answer:
Test Cross

8. Linked genes are present on the …………………………….. .
Answer:
Same Chromosome

III. One Word Answer Questions

Question 1.
On which plant did Mendel carry out his experiments?
Answer:
Garden pea (Pisum sativum).

Question 2.
Who is called the Father of Genetics?
Answer:
G. J. Mendel

Question 3.
What is the phenotypic ratio of F₂ in a dihybrid cross?
Answer:
9 : 3 : 3: 1

Question 4.
What is the genotypic ratio of F₂ in a monohybrid cross?
Answer:
1:2:1

Question 5.
What is meant by a physically expressed external character of an individual?
Answer:
Phenotype

Question 6.
What is known as having two similar alleles for a particular trait?
Answer:
Homozygous

Question 7.
What is the term used for the discrete units that govern inheritance of characters?
Answer:
Factors

Question 8.
Mention one cross in which the phenotypic ratio is the same as the genotypic ratio in the F generation.
Answer:
Incomplete dominance or Co-dominance.

Objective Questions

Question 1.
Genes responsible for a pair of opposite traits are known as
1. Hybrids
2. Factors
3. Purehnes
4. Alleles
Answer:
4. Alleles

Question 2.
The dwarf character appears
1. Only after selfing the F₁ hybrids
2. Only in F₁ generation
3. After crossing F₁ hybrids with the dominant parent
4. Only in F₂ generation
Answer:
1. Only after selfing the F₁ hybrids

Question 3.
In Snapdragon, inheritance of flower colour demonstrates
1. Complete dominance
2. Incomplete recessiveness
3. Incomplete dominance
4. Complete recessiveness
Answer:
3. Incomplete dominance

Question 4.
The Law of Independent Assortment is best explained by
1. Test cross
2. Dihybrid cross
3. Monohybrid cross
4. Backcross
Answer:
2. Dihybrid cross

Question 5.
In Drosophila, the genes controlling body colour and eye colour are located on
1. Sex chromosome
2. X chromosome
3. Autosomes
4. Y chromosome
Answer:
3. Autosomes

Question 6.
The chromosome mapping technique was introduced by
1. Alfred Sturtevant
2. Franklin Stahl
3. Marshall Nirenberg
4. Alfred Hershey
Answer:
1. Alfred Sturtevant

Question 7.
A point mutation refers to
1. Loss of chromosome segments
2. Addition of new chromosome segments
3. Change in a single DNA base pair
4. Alteration of an entire chromosome set
Answer:
3. Change in a single DNA base pair

Question 8.
Sickle-cell anaemia results from
1. Polyploidy
2. Single base alteration
3. Insertion
4. Deletion
Answer:
2. Single base alteration

Question 9.
In agriculture, mutations are useful for
1. Development of improved varieties
2. Weed control
3. Pest control
4. Pathogen control
Answer:
1. Development of improved varieties

Question 10.
Which of the following traits in pea plants is recessive?
1. Tall plants
2. Yellow-coloured pods
3. Round seeds
4. Axial flowers
Answer:
2. Yellow-coloured pods

Question 11.
The fastest method of generating genetic variation in crop plants is
1. Polyploidy
2. Hybridization
3. Mutation
4. Selfing
Answer:
3. Mutation

Question 12.
The major chemical basis of heredity in living organisms is
1. Protein
2. DNA
3. Enzyme
4. RNA
Answer:
2. DNA

Question 13.
Genetic information is stored in DNA instead of RNA because
1. DNA is more stable
2. DNA is double-stranded
3. DNA can replicate
4. DNA has higher molecular weight
Answer:
1. DNA is more stable

Question 14.
Genomics is a modern branch concerned with
1. Study of genes
2. Artificial synthesis of genes
3. Transfer of hereditary information
4. Study of the nucleotide sequence of the human genome
Answer:
4. Study of the nucleotide sequence of the human genome

Question 15.
Identify the correct statement
1. Variations are caused only by mutations
2. Hereditary material in all organisms is DNA
3. Genes are randomly arranged on chromosomes
4. RNA is a highly stable nucleic acid
Answer:
2. Hereditary material in all organisms is DNA

Question 16.
The fundamental unit of inheritance is
1. DNA
2. Chromosome
3. Gene
4. Nucleus
Answer:
3. Gene

Question 17.
Mutations bring changes in
1. Genotype only
2. Phenotype only
3. Chromosomes only
4. Both genotype and phenotype
Answer:
4. Both genotype and phenotype

Question 18.
Mutations do not lead to
1. Variations
2. Cancer
3. Changes in gene sequences
4. Denaturation of DNA molecule
Answer:
4. Denaturation of DNA molecule

Question 19.
Transgenic crops are produced through
1. Hybridization
2. Gene transfer
3. Gene sequencing
4. Induced mutations
Answer:
2. Gene transfer

Question 20.
Variation and recombination mainly arise due to
1. Cytokinesis
2. Crossing over
3. Synapsis
4. Disjunction of genomes
Answer:
2. Crossing over

Question 21.
Linked genes can be separated naturally through
1. Mutation
2. Genetic engineering
3. Crossing over
4. Genomics
Answer:
3. Crossing over

Question 22.
Which one of the following is NOT a characteristic of genetic material?
1. It should be able to mutate
2. It should replicate itself
3. It is chemically more reactive
4. It must be stable
Answer:
3. It is chemically more reactive

Question 23.
Among the following, which acts as the genetic material?
1. Histone
2. DNA
3. Protein
4. Non-histone
Answer:
2. DNA

Question 24.
Mutations are
1. Non-heritable changes
2. Heritable alterations in characters
3. Changes only in chromosome number
4. Changes only in chromosome shape
Answer:
2. Heritable alterations in characters

Question 25.
Parental characters appear in offspring because of
1. Recombinations
2. Mutation
3. Linkage
4. Crossing
Answer:
3. Linkage

Question 26.
A true-breeding plant is one that
1. Is always homozygous recessive
2. Produces offspring by selfing and remains homozygous
3. Breeds on its own
4. Is produced by selfing a heterozygous plant
Answer:
2. Produces offspring by selfing and remains homozygous

Question 27.
Normally, a gamete contains
1. Many alleles of a gene
2. One allele of a gene
3. All alleles of a gene
4. Two alleles of a gene
Answer:
2. One allele of a gene

Question 28.
Mendel proposed that stable units passed from parents to offspring are called
1. Genes
2. Alleles
3. Factors
4. Genotype
Answer:
3. Factors

Question 29.
In a dihybrid cross, the maximum number of phenotypes that can be obtained is
1. 8
2. 16
3. 4
4. 2
Answer:
3. 4

Question 30.
The numbers of genotypes and phenotypes, respectively, in the F₂ generation of a Mendelian dihybrid cross are
1. 4 & 9
2. 9 & 4
3. 8 & 16
4. 9 & 12
Answer:
2. 9 & 4

Question 31.
What is the phenotypic ratio obtained in a dihybrid test cross?
1. 9 : 3 : 3: 1
2. 1: 1: 1: 1
3. 2: 1: 1
4. 1 : 2 : 2 : 4 : 1 : 2 : 1 : 2 : 1
Answer:
2. 1: 1: 1: 1

Question 32.
A cross between two pea plants with round seeds produced some wrinkled-seeded offspring. The parental genotypes must be
1. RR & RR
2. RR & Rr
3. Rr & Rr
4. RR & rr
Answer:
2. RR & Rr

Question 33.
A change occurring in a single base pair of DNA is known as
1. Silent mutation
2. Point mutation
3. Frame-shift mutation
4. Lethal mutation
Answer:
2. Point mutation

Question 34.
A well-known example of a point mutation is
1. Turner’s syndrome
2. Down’s syndrome
3. Sickle-cell anaemia
4. Acquired Immunodeficiency Syndrome
Answer:
3. Sickle-cell anaemia

Question 36.
If all F₁ plants are tall and the F₂ generation shows a 3 tall: 1 dwarf ratio, it supports
1. Law of Dominance
2. Law of Segregation
3. Law of Independent Assortment
4. Incomplete Dominance
Answer:
2. Law of Segregation

Question 37.
In the F₂ generation, both phenotypic and genotypic ratios are 1: 2 :1 in
1. Codominance
2. Incomplete dominance
3. Test cross
4. 1 & 2
Answer:
4. 1 & 2

Question 38.
In a monohybrid cross, F₁ hybrids produce two types of gametes carrying one character each. This illustrates
1. Alleles
2. Heterozygous condition
3. Purity of gametes
4. Inherited factor
Answer:
3. Purity of gametes

Question 39.
When a heterozygous tall plant is crossed with a homozygous dwarf plant, the progeny shows
I) 1: 1 phenotypic ratio
II) 1: 1 genotypic ratio
III) No recessive individuals
IV) No dominant individuals
1. I & II
2. I & IV
3. I & III
4. III & IV
Answer:
1. I & II

Question 40.
The diagrammatic tool used to visualize all possible combinations of male and female gametes is called
1. Morgan square
2. Punnett square
3. Bateson square
4. Mendel square
Answer:
2. Punnett square

Question 41.
A cross between an organism showing a dominant trait and another with a known recessive phenotype is called
1. Back cross
2. Reciprocal cross
3. Test cross
4. Progeny test
Answer:
3. Test cross

Question 42.
In a typical monohybrid cross, the percentage of F₂ offspring resembling the dominant parent phenotypically is
1. 25
2. 75
3. 50
4. 100
Answer:
2. 75

Question 43.
The Mendelian phenotypic ratio of 9 :3 : 3: 1 is explained by
1. Law of Dominance
2. Law of Segregation
3. Law of Purity of Gametes
4. Law of Independent Assortment
Answer:
4. Law of Independent Assortment

Question 44.
How many different types of gametes can be produced by a plant with genotype Yy rrTt?
1. Two
2. One
3. Four
4. Eight
Answer:
3. Four

Question 45.
The famous paper “Experiments on Plant Hybrids” was published in
1. 1866
2. 1856
3. 1863
4. 1906
Answer:
4. 1906

Question 46.
Gene → ⊗ → Character. Identify X.
1. Toxin
2. Hormone
3. Vitamin
4. Enzyme
Answer:
4. Enzyme

Question 47.
The 3: 1 proportion observed in the F₃ generation is explained by
1. Law of Segregation
2. Law of Dominance
3. Test Cross
4. Law of Independent Assortment
Answer:
1. Law of Segregation

Question 48.
When both alleles express their effects simultaneously in a heterozygote, the phenomenon is known as
1. Dominance
2. Codominance
3. Pseudodominance
4. Amphidominance
Answer:
2. Codominance

Question 49.
Which one of the following represents a test cross?
1. YyRr × yyrr
2.YYRR × yyrr
3.YyRr × YyRr
4.YyRr × YYYR
Answer:
1. YyRr × yyrr

Question 50.
A test cross is mainly carried out to determine the
1. Phenotype of hybrid
2. Genotype of hybrid
3. Genotype of recessive parent
4. Genotype of dominant parent
Answer:
4. Genotype of dominant parent

Question 51.
No phenotypic change occurs when an altered gene produces
1. No enzyme
2. Functional enzyme
3. Less efficient enzyme
4. Non-functional enzyme
Answer:
4. Non-functional enzyme

Question 52.
Pleiotropy is correctly represented as
1. One gene → one phenotype
2. One phenotype → different genotypes
3. One gene → different phenotypes
4. Many genes → one phenotype
Answer:
3. One gene → different phenotypes

Question 53.
Phenotypic and genotypic ratios differ in
1. Monohybrid cross F₂
2. Monohybrid Test Cross
3. Codominance F₂
4. Incomplete Dominance F₂
Answer:
1. Monohybrid cross F₂

Question 54.
The stage of meiosis during which chromosome segregation occurs is
1. Prophase I
2. Anaphase I
3. Prophase II
4. Anaphase II
Answer:
2. Anaphase I

Question 55.
Crossing over in diploid organisms is mainly responsible for
1. Dominance of genes
2. Linkage between genes
3. Recombination of linked genes
4. Segregation of alleles
Answer:
3. Recombination of linked genes

Question 56.
According to Mendelism, which of the following shows dominance?
1. Wrinkled seeds
2. Green seed coat colour
3. Green pod colour
4. Terminal flower position
Answer:
3. Green pod colour

Question 57.
In hybridization, Tt × tt produces offspring in the ratio
1. 3: 1
2. 1: 2: 1
3. 1: 1
4. 1: 2
Answer:
3. 1: 1

Question 58.
Multiple alleles are responsible for the Inheritance of
1. Phenylketonuria
2. Colour blindness
3. ABO blood groups
4. Sickle-cell anaemia
Answer:
3. ABO blood groups

Question 59.
The process that enables a gene to move from one linkage group to another is called
1. Duplication
2. Inversion
3. Crossing-over
4. Translocation
Answer:
4. Translocation

Question 60.
Fruit colour in squash is an example of
1. Recessive epistasis
2. Dominant epistasis
3. Complementary genes
4. Inhibitory genes
Answer:
2. Dominant epistasis

Reviewing AP Inter 2nd Year Botany Study Material Chapter 1 Sexual Reproduction in Flowering Plants Questions and Answers can help students prepare confidently for exams.

AP Inter 2nd Year Botany 1st Lesson Sexual Reproduction in Flowering Plants Questions and Answers

IV. Very Short Answer Questions

Question 1.
Name the parts of an angiosperm flower where the development of male and female gametophytes takes place?
Answer:

1. The male gametophyte develops from microspores inside the anther.
2. The female gametophyte develops from the megaspore inside the ovule of the ovary.

Question 2.
What is the role of tapetum in the development of pollen grains?
Answer:

1. The tapetum supports pollen development by supplying nutrients and enzymes to the developing microspores.
2. It also helps in the growth and maturation of pollen grains.

Question 3.
Which cells are present in a pollen grain when it is shed at the three-celled stage?
Answer:
A pollen grain released at the three-celled stage contains one vegetative (tube) cell, Two male gametes (sperm cells).

Question 4.
Name the component cells of the egg apparatus in an embryo sac.
Answer:
The egg apparatus consists of three cells:

1. One egg cell,
2. Two synergids.

Question 5.
What is meant by monosporic development of the female gametophyte?
Answer:
Formation of the embryo sac from one functional megaspore is called monosporic development.

Question 6.
Differentiate between cleistogamy and chasmogamy?
Answer:

Question 7.
Differentiate between geitonogamy and xenogamy?
Answer:

Question 8.
How does pollination occur in water plants?
Answer:
Pollination in aquatic plants occurs in two ways:

1. Epihydrophily: Pollination takes place on the water surface. Ex: Vallisneria
2. Hypohydrophily: Pollination takes place below the water surface. Ex: Zostera

Question 9.
What is self-incompatibility?
Answer:

1. Self-incompatibility is the inability of pollen grains to germinate or grow on the stigma of the same flower or a genetically similar flower.
2. Ex: Brassica

Question 10.
Name the parts of the pistil that develop into fruit and seeds.
Answer:

1. After fertilization, the ovary enlarges and develops into the fruit.
2. The ovules develop into seeds.

Question 11.
What is meant by polyembryony?
Answer:

1. Polyembryony is the formation of more than one embryo inside a single seed.
2. These embryos may arise from the zygote or from other tissues such as the nucellus or integuments. Ex: Citrus, Mango.

Question 12.
What is scutellum? In which type of seeds is it found?
Answer:

1. Scutellum is a large, shield-shaped cotyledon present in the embryo.
2. It is found in monocot seeds, especially in grasses.

V. Short Answer Questions

Question 1.
With the help of a neat labelled diagram, describe the structure of megasporangium?
Answer:
The megasporangium (ovule) is a small reproductive structure present inside the ovary of a flower. An atypical angiosperm ovule consists of the following parts:

1. Funicle: The funicle is the stalk that connects the ovule to the placenta.
2. Hilum: The hilum is the point where the body of the ovule joins the funicle.
3. Integuments: These are one or two protective coverings surrounding the nucellus, leaving a small opening at one end. Later, they develop into the seed coat.
4. Micropyle: The micropyle is a tiny opening at the tip of the ovule through which the pollen tube enters during fertilization.
5. Chalaza: The chalaza is the basal region of the ovule situated opposite to the micropyle.
6. Nucellus: The nucellus is a nutritive tissue enclosed by the integuments. It provides nourishment to the developing embryo sac.
7. Embryo Sac: The embryo sac is the female gametophyte present inside the nucellus. It is usually 7-celled and 8-nucleate and develops from a megaspore.

Question 2.
Write a brief note on different kinds of pollination?
Answer:
Pollination is the transfer of pollen grains from the anther to the stigma of a flower, which is essential for fertilization.

Based on the source of pollen, pollination is classified into three types:
1. Autogamy: Autogamy is the transfer of pollen from the anther to the stigma of the same flower. Occurs mainly in bisexual flowers. Does not require any external pollinating agent. Ensures self-pollination and guaranteed seed formation. Ex: Pea, Wheat

2. Geitonogamy: Geitonogamy is the transfer of pollen from one flower to another flower on the same plant. Requires pollinating agents such as insects or wind. Functionally resembles cross-pollination. Genetically similar to self-pollination. Ex: Maize, Cucurbits

3. Xenogamy: Xenogamy is the transfer of pollen from a flower of one plant to the stigma of a flower on a different plant of the same species. Always requires external pollinating agents. Produces genetic variation in offspring. Ex: Papaya, Date Palm.

Question 3.
Explain different types of outbreeding devices to encourage cross-pollination.
Answer:
Outbreeding devices are special adaptations in flowering plants that prevent self-pollination and promote cross-pollination.
1. Non-Synchronization: In some plants, pollen release and stigma receptivity do not occur at the same time. Pollen may be released before the stigma becomes receptive. Or the stigma may become receptive before pollen release. This prevents self-pollination. Ex: Ivy

2. Spatial Separation: The anthers and stigma are located at different positions in the flower. This arrangement reduces the chance of self-pollination. Ex: Oxalis

3. Self-Incompatibility: It is a genetic mechanism that prevents self-pollen from fertilizing the ovule.It may stop pollen germination. It may inhibit pollen tube growth. Ex: Petunia

4. Production of Unisexual Flowers:

• Monoecious Plants: Male and female flowers are present on the same plant. Prevents autogamy but not geitonogamy. Ex: Maize, Castor
• Dioecious Plants: Male and female flowers occur on different plants. Prevents both autogamy and geitonogamy. Ex: Papaya

Question 4.
Discuss pollen-pistil interactions.
Answer:
Pollen-pistil interaction refers to the series of events that occur after pollen lands on the stigma and continues until the pollen tube enters the ovule. Important Steps in Pollen-Pistil Interaction.

1. Recognition and Interaction: The pistil identifies whether the pollen grain is compatible or incompatible. This recognition occurs through chemical signals between pollen and stigma.
2. Acceptance or Rejection: If the pollen is compatible, the pistil accepts it and supports its growth.
   If incompatible, the pollen is rejected by preventing germination or pollen tube growth.
3. Pollen Germination and Pollen Tube Growth: Accepted pollen grains germinate on the stigma. A pollen tube develops through a germ pore. In 2-celled pollen: The generative cell divides to form two male gametes during pollen tube growth. In 3-celled pollen, two male gametes are already present.
4. Entry into the Ovule: The pollen tube enters the ovule through the micropyle. It penetrates one of the synergids. The filiform apparatus guides the pollen tube toward the egg apparatus.

Question 5.
Explain the process of artificial hybridization.
Answer:
Artificial hybridization is a technique used in plant breeding to combine desirable traits from different parent plants. It ensures that only selected pollen grains participate in pollination. Steps Involved in Artificial Hybridization

1. Emasculation: In bisexual flowers, anthers are removed before they release pollen. This prevents self-pollination.
2. Bagging: The emasculated flower is covered with a bag, usually made of butter paper. This prevents unwanted pollen from reaching the stigma.
3. Pollination: When the stigma becomes receptive, pollen grains from the selected male parent are collected and dusted onto it.
4. Rebagging: After pollination, the flower is covered again. This prevents contamination by unwanted pollen. The cover is kept until fruit development begins.

Question 6.
How is endosperm formed in flowering plants?
Answer:
Endosperm formation occurs as a result of double fertilization in flowering plants.

Formation of endosperm: Two male gametes are released into the embryo sac. One male gamete fuses with the egg cell to form the zygote (syngamy). The second male gamete fuses with the two polar nuclei in the central cell. This fusion is called triple fusion and forms the Primary Endosperm Nucleus (PEN), which is triploid.

Development and Functions

1. Nutritional Role: Endosperm supplies food to the developing embryo. It generally develops before the embryo.
2. Modes of Development: In many plants, PEN undergoes repeated nuclear divisions without cell wall formation. This stage is known as free-nuclear endosperm. Later, cell walls are formed, producing cellular endosperm. Ex: In coconut, coconut water represents free-nuclear endosperm, while the white kernel represents cellular endosperm.
3. Persistence in Seeds: In non-albuminous seeds such as Pea and Groundnut, the endosperm is consumed during seed development. In albuminous seeds such as Wheat, Maize, and Castor, the endo sperm remains in the mature seed.

Question 7.
Describe the structure of dicot embryo with the help of a neat labelled diagram?
Answer:
A typical dicot embryo is made up of an embryonal axis and two cotyledons.

1. Cotyledons: A dicot embryo contains two cotyledons. They store and supply food to the developing embryo.
2. Embryonal Axis: The embryonal axis is the central part of the embryo situated between the two cotyledons.
3. Epicotyl: The portion of the embryonal axis above the cotyledons is called the epicotyl. It ends in the plumule, which develops into the shoot system
4. Hypocotyl: The portion of the embryonal axis below the cotyledons is called the hypocotyl. It terminates in the radicle, which later develops into the primary root.
5. Plumule: The plumule is the growing shoot tip of the embryo. It gives rise to the future stem and leaves.
6. Radicle: The radicle is the embryonic root. It develops into the primary root of the plant.
7. Root Cap: The tip of the radicle is covered by a root cap. It protects the delicate root tip during growth.

Question 8.
What is apomixis and what is its importance?
Answer:
Apomixis is the formation of seeds without fertilization. It is a type of asexual reproduction in plants.
Apomixis occurs when a diploid egg cell develops into an embryo without undergoing meiosis and fertilization. Seed formation can occur even when pollinators are absent or environmental conditions are unfavorable.

Importance of Apomixis:

1. No Segregation of Characters: Since meiosis and fertilization do not occur, desirable traits remain unchanged.
2. Maintenance of Superior Traits: Valuable characteristics can be preserved for many generations.
3. Useful in Agriculture: Helps maintain hybrid vigour (heterosis). Beneficial for large-scale commercial seed production.

VI. Long Answer Questions

Question 1.
Describe the structure of anther with the help of a neat diagram?
Answer:

1. A typical angiosperm anther is a bilobed structure, and each lobe contains two thecae, making it dithecous.
2. As the anther matures, the microsporangia develop into pollen sacs, which extend along the length of the anther and contain numerous pollen grains.

1. External Structure :

• Stamen The stamen is the male reproductive organ of a flower. It consists of an anther and a filament. The anther is the fertile terminal part, while the filament is the slender stalk that supports it.
• Bilobed and Dithecous: An atypical angiosperm anther is bilobed, meaning it has two distinct lobes. Each lobe contains two chambers (thecae), making the anther dithecous.
• Tetragonal Structure: In transverse section (T.S.), the anther appears tetragonal (four-sided). A microsporangium is present at each corner, giving a total of four microsporangia, with two in each lobe.

2. Internal Structure of Microsporangium: Each microsporangium is nearly circular and is surrounded by four wall layers.

Wall Layers :

• Epidermis: The epidermis is the outermost protective layer of the microsporangium.
• Endothecium: Located just below the epidermis, the endothecium helps in the dehiscence (opening) of the anther for pollen release.
• Middle Layers: These layers lie between the endothecium and tapetum and provide additional protection. They usually degenerate as the anther matures.
• Tapetum: The tapetum is the innermost layer and supplies nourishment to the developing pollen grains. Its cells are dense and often multinucleate.

Sporogenous Tissue: In a young anther, the central region of each microsporangium contains compact, homogeneous cells called sporogenous tissue. These cells undergo meiosis to form microspores, which later develop into pollen grains.

Function of Outer Layers: The epidermis, endothecium, and middle layers protect the microsporangium and assist in anther dehiscence for pollen release.

3. Maturation and Dehiscence

• Pollen Sac Formation: As development proceeds, the microsporangia transform into pollen sacs extending throughout the anther.
• Pollen Development: Microspores separate from the tetrads and mature into individual pollen grains.
• Dehiscence (Release): When the anther becomes fully mature, it splits open and releases pollen grains into the environment.

Question 2.
Describe briefly the process of microsporogenesis and development of male gametophyte in angiosperms?
Answer:
Microsporogenesis and male gametophyte development are important reproductive processes occurring inside the microsporangia of the anther.
1. Microsporogenesis: Microsporogenesis is the formation of microspores from a pollen mother cell (PMC) through meiosis.

• Initial Stage: In a young anther, each microsporangium contains sporogenous tissue made up of compact cells.
• Meiotic Division: Each sporogenous cell functions as a PMC and undergoes meiosis to produce haploid cells.
• Formation of Tetrads: Meiosis results in the formation of four haploid microspores, which remain attached as a tetrad.
• Maturation: As the anther matures, microspores separate from the tetrad and become individual pollen grains.

2. Development of Male Gametophyte: The pollen grain represents the male gametophyte. Its development involves structural and cellular changes before fertilization.

• Structure of Pollen Grain: Pollen grains are generally spherical, measuring about 25-50 micrometers in diameter.
• Exine: The outer hard wall is called exine and is made of sporopollenin, one of the most resistant organic substances. Germ pores are present where sporopollenin is absent.
• Intine: The intine is the inner thin wall made of cellulose and pectin.
• Cytoplasm: The cytoplasm contains all the essential cell components required for growth and development.

3. Cellular Development: As the pollen grain matures, it divides internally to form two cells.

• Vegetative Cell: The larger cell of the pollen grain containing abundant food reserves. It helps in pollen tube formation.
• Generative Cell: A smaller spindle-shaped cell present within the vegetative cell. It later divides to form two male gametes.

4. Shedding Stages:

• 2-Cell Stage: In most angiosperms, pollen grains are shed with two cells—a vegetative cell and a generative cell. The generative cell divides later.
• 3-Celled Stage: In some species, the generative cell divides before shedding, so the pollen grain contains one vegetative cell and two male gametes.

Question 3.
Describe the process of megasporogenesis and development of embryo sac?
Answer:
1. Megasporogenesis: Megasporogenesis is the process by which megaspores are formed from a Megaspore Mother Cell (MMC) inside the ovule.

• Location: Within the nucellus, near the micropylar region, a cell differentiates into the MMC.
• Characteristics of MMC: The MMC is a large cell with dense cytoplasm and a prominent nucleus, specialized for division.
• Meiotic Division: The MMC undergoes meiosis, reducing the chromosome number from diploid to haploid. As a result, four haploid megaspores are formed, usually arranged in a linear row.

2. Development of Embryo Sac: After megasporogenesis, the megaspores develop into the female gametophyte or embryo sac.

• Functional Megaspore: Out of the four megaspores, only one remains functional, while the other three degenerate. This is called monosporic development.
• Nuclear Divisions: The nucleus of the functional megaspore undergoes three successive mitotic divisions:

First division → 2-nucleate stage
Second division → -nucleate stage
Third division → 8-nucleate stage

These are free nuclear divisions because cell walls are not formed immediately.
Cellular Organization: After the 8-nucleate stage, cell walls develop, resulting in a properly organized embryo sac.

3. Structure of Mature Embryo Sac: A Mature embryo sac is 8-nucleate and 7-celled.

• Egg Apparatus (Micropylar End): Consists of one egg cell and two synergids. The synergids possess a filiform apparatus that guides the pollen tube.
• Antipodal Cells (Chalazal End): Three antipodal cells are present at the opposite end of the embryo sac.
• Central Cell: The large central cell contains two polar nuclei, which participate in triple fusion.

Question 4.
Define pollination and give an account of agents of pollination.
Answer:
Pollination is the transfer of pollen grains from the anther to the stigma of a flower, leading to fertilization
Pollination occurs through different agents, broadly classified as abiotic agents (wind and water) and biotic agents (animals).

Agents of Pollination:
1. Wind Pollination (Anemophily): Pollination by wind is called anemophily.
Characteristics:

• Pollen grains are light, dry, and non-sticky.
• Flowers produce large quantities of pollen.
• Stamens remain exposed for easy pollen release.
• Stigmas are large and feathery to trap pollen.
• Flowers are often arranged in inflorescences. Examples: Maize, Grasses

2. Water Pollination (Hydrophily): Pollination through water is called hydrophily.
a) Epihydrophily: Pollination occurs on the water surface.

• Female flowers reach the surface through long stalks.
• Male flowers float and are carried by water currents. Example: Vallisneria

b) Hypohydrophily: Pollination occurs below the water surface.

• Flowers remain submerged.
• Pollen grains are long and ribbon-like. Example: Zostera

3. Animal Pollination (Zoophily): Pollination by animals is called zoophily.
Characteristics:

• Flowers are brightly coloured and fragrant.
• Nectar is produced to attract animals.
• Pollen grains are sticky.

Types of Zoophily:

• Entomophily – Pollination by insects
• Ornithophily – Pollination by birds
• Chiropterophily- pollination by bats
• Therophily – Pollination by small mammals
• Ophiophily-Pollination by reptiles (rare). Ex: Squirrels.

Question 5.
Describe the fertilization process in angiosperms.
Answer:
Fertilization is the fusion of male and female gametes. In angiosperms, fertilization is unique because it involves double fertilization.

Steps of Fertilization:
1. Entry of Pollen Tube into Ovule: The pollen tube may enter the ovule through different routes:

• Porogamy: Entry through the micropyle. Ex: Hibiscus
• Chalazogamy: Entry through the chalaza. Ex: Casuarina
• Mesogamy: Entry through the integuments. Ex Cucurbita

2. Entry into Embryo Sac: The pollen tube enters the embryo sac through the micropyle. The filiform apparatus of the synergids guides the pollen tube to its destination.

3. Release of Male Gametes: The pollen tube enters one synergid and bursts, releasing two male gametes into the embryo sac.

4. Syngamy: One male gamete fuses with the egg cell to form a diploid zygote. This process is called syngamy (true fertilization).

5. Triple Fusion and Double Fertilization:

• Triple Fusion: The second male gamete fuses with the two polar nuclei present in the central cell, forming a triploid Primary Endosperm Nucleus (PEN).
• Double Fertilization: Since syngamy and triple fusion occur together, the process is called double fertilization.

I. Multiple Choice Questions

Question 1.
Identify the correct sequence of anther wall layers from inside to the outside of an anther lobe.
1. the epidermis – endothecium – middle layers – tapetum
2. the epidermis – middle layers – endothecium – tapetum
3. the tapetum – middle layers – endothecium – epidermis
4. the tapetum – endothecium – middle layers – epidermis
Answer:
3. the tapetum – middle layers – endothecium – epidermis

Question 2.
The male gametophyte in flowering plants is represented by?
1. anther
2. microspore mother cell
3. stamen
4. pollen grain
Answer:
4. pollen grain