Principles of Inheritance and Variation

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CBSE Learning Objectives – Key Concepts & Skills You Must Know

Learning Objectives

Understand the principles of inheritance as established by Mendel.
Explain the structure and function of DNA in relation to genetic inheritance.
Describe the mechanisms of evolution and their molecular basis.
Analyze the role of mutations in genetic variation and disorders.
Differentiate between dominant and recessive traits, as well as homozygous and heterozygous genotypes.
Apply Mendel's laws to predict genetic outcomes using Punnett squares.
Conduct pedigree analysis to trace inheritance patterns in families.
Discuss the implications of polygenic inheritance and pleiotropy in genetics.
Explore the concept of sex determination and its genetic basis.

CBSE Revision Notes & Quick Summary for Last-Minute Study

Chapter 4: Principles of Inheritance and Variation

Overview

The work of Mendel established the idea of inheritance patterns.
The nature of 'factors' determining phenotype was initially unclear.
Understanding genetic material structure became a focus in biology.

Key Concepts

Mendel's Laws of Inheritance

Law of Dominance: Dominant traits are expressed in heterozygous conditions.
Law of Segregation: Alleles segregate during gamete formation.
Law of Independent Assortment: Genes assort independently during gamete formation.

Genetic Terms

Genotype: Genetic makeup of an organism.
Phenotype: Physical expression of traits.
Alleles: Different forms of a gene.

Genetic Disorders

Down's Syndrome: Trisomy of chromosome 21 (47 chromosomes total).
Turner's Syndrome: Missing X chromosome (XO).
Klinefelter's Syndrome: Extra X chromosome (XXY).

Mutation

Point Mutation: Change in a single base pair (e.g., sickle cell anemia).
Chromosomal Aberrations: Changes in chromosome structure or number.

Pedigree Analysis

A method to trace inheritance patterns in families.
Useful for understanding genetic disorders.

Polygenic Inheritance

Traits controlled by multiple genes (e.g., human height, skin color).
Phenotype reflects the additive effect of alleles.

Pleiotropy

A single gene affecting multiple traits (e.g., phenylketonuria).

Sex Determination

Genetic basis of sex determination observed in insects.
Chromosomes play a key role in determining sex.

CBSE Exam Tips, Important Questions & Common Mistakes to Avoid

Common Mistakes and Exam Tips

Common Pitfalls

Misunderstanding Dominance: Students often confuse dominant and recessive traits. Remember that dominant traits are expressed in heterozygous conditions, while recessive traits are only expressed in homozygous conditions.
Confusing Segregation and Assortment: The Law of Segregation refers to the separation of alleles during gamete formation, while the Law of Independent Assortment pertains to the independent distribution of different genes during gamete formation.
Ignoring Linkage: Not all genes assort independently; linked genes are located on the same chromosome and do not follow the Law of Independent Assortment.
Overlooking Mutations: Students may forget that mutations can be point mutations (single base changes) or larger chromosomal alterations. Understanding the implications of these mutations is crucial.

Tips for Exam Preparation

Use Punnett Squares: Practice using Punnett Squares to visualize genetic crosses and predict phenotypic ratios.
Familiarize with Pedigree Analysis: Understand how to read and construct pedigree charts, as they are essential for tracking inheritance patterns in humans.
Review Mendel's Laws: Ensure you can clearly explain Mendel's Laws of Inheritance, including the Law of Dominance and the Law of Segregation.
Practice with Genetic Disorders: Be prepared to discuss examples of genetic disorders, their inheritance patterns, and the underlying genetic mechanisms.

CBSE Quiz & Practice Test – MCQs, True/False Questions with Solutions

Multiple Choice Questions

Round

Wrinkled

Oval

Flat

Correct Answer: A

Solution:

In Mendel's experiments, the round seed shape was the dominant trait over wrinkled.

22 pairs of autosomes and XX

22 pairs of autosomes and XY

23 pairs of autosomes

22 pairs of autosomes and YY

Correct Answer: B

Solution:

A normal human male has 22 pairs of autosomes and one pair of sex chromosomes, XY.

IAIA and IBIB

IAi and IBi

IAIA and IBi

IAi and IBIB

Correct Answer: B

Solution:

For a child to have blood group O, both parents must carry the recessive allele 'i'. Thus, the possible genotypes are IAi for the father and IBi for the mother.

0% recombination frequency

50% recombination frequency

100% recombination frequency

25% recombination frequency

Correct Answer: B

Solution:

Genes that are far apart on the same chromosome are likely to assort independently, resulting in a recombination frequency close to 50%.

A change in the entire chromosome number

A change of a single base pair in DNA

A deletion of a chromosome segment

A duplication of a chromosome segment

Correct Answer: B

Solution:

A point mutation is defined as a change of a single base pair in DNA.

22 pairs of autosomes and XY

22 pairs of autosomes and XX

23 pairs of autosomes and XX

23 pairs of autosomes and XY

Correct Answer: B

Solution:

A normal human female has 22 pairs of autosomes and a pair of sex chromosomes (XX).

The genes are linked on the same chromosome.

The genes assort independently.

The genes show incomplete dominance.

The genes are sex-linked.

Correct Answer: B

Solution:

A 9:3:3:1 phenotypic ratio in the F2 generation is indicative of independent assortment, as described by Mendel's Law of Independent Assortment.

Trisomy of chromosome 21

Monosomy of chromosome X

Trisomy of chromosome 18

Monosomy of chromosome 22

Correct Answer: A

Solution:

Down's syndrome is caused by the presence of an extra copy of chromosome 21, resulting in trisomy.

Green

Yellow

White

Round

Correct Answer: B

Solution:

In Mendel's experiments, yellow seed color was considered the dominant trait.

Incomplete dominance

Co-dominance

Pleiotropy

Epistasis

Correct Answer: C

Solution:

This scenario is an example of pleiotropy, where a single gene influences multiple phenotypic traits.

Gregor Mendel

Thomas Hunt Morgan

Walter Sutton

Theodore Boveri

Correct Answer: B

Solution:

Thomas Hunt Morgan and his colleagues provided experimental verification of the chromosomal theory of inheritance.

Turner's syndrome

Klinefelter's syndrome

Down's syndrome

Polyploidy

Correct Answer: C

Solution:

Down's syndrome is characterized by trisomy of chromosome 21, resulting in a total of 47 chromosomes in the cell.

All red flowers

All white flowers

All pink flowers

Red and white flowers in a 1:1 ratio

Correct Answer: C

Solution:

In incomplete dominance, the F1 generation exhibits a blend of the parental traits. Thus, crossing a homozygous red-flowered plant with a homozygous white-flowered plant results in all F1 offspring having pink flowers.

25%

50%

75%

100%

Correct Answer: A

Solution:

In an autosomal recessive disorder, two carrier parents (Aa x Aa) have a 25% chance of having an affected child (aa).

25%

50%

75%

100%

Correct Answer: A

Solution:

If both parents are carriers (heterozygous) of an autosomal recessive disorder, there is a 25% probability that their child will inherit two recessive alleles and be affected by the disorder.

9:3:3:1

3:1

9:3:4

1:1:1:1

Correct Answer: A

Solution:

The cross between RrYy and RrYY involves two traits with independent assortment, leading to a phenotypic ratio of 9:3:3:1.

9:3:3:1

3:1

1:1:1:1

1:2:1

Correct Answer: A

Solution:

The expected phenotypic ratio for a dihybrid cross involving two heterozygous parents (GgSs x GgSs) with unlinked loci is 9:3:3:1. This ratio represents the combination of dominant and recessive traits for both characteristics.

Polyploidy

Aneuploidy

Monosomy

Trisomy

Correct Answer: B

Solution:

Aneuploidy refers to the gain or loss of one or more chromosomes, resulting in an abnormal chromosome number.

Gregor Mendel

Thomas Hunt Morgan

Walter Sutton

Theodore Boveri

Correct Answer: B

Solution:

Thomas Hunt Morgan used fruit flies (Drosophila melanogaster) to study genetic inheritance and contributed to the chromosomal theory of inheritance.

9:3:3:1

3:1

1:1

1:2:1

Correct Answer: C

Solution:

If the genes are linked and no recombination occurs, the expected phenotypic ratio would be 1:1 for the parental types.

A change in the number of chromosomes

A substitution of a single base pair in DNA

A deletion of a large segment of DNA

An inversion of a chromosome segment

Correct Answer: B

Solution:

A point mutation is defined as a change in a single base pair in DNA, which can lead to disorders such as sickle-cell anemia.

9:3:3:1

3:1

8:4:4:1

10:2:2:1

Correct Answer: C

Solution:

The recombination frequency of 20% indicates that 80% of the offspring will show parental phenotypes and 20% will show recombinant phenotypes, leading to a ratio close to 8:4:4:1.

Autosomal recessive

Autosomal dominant

X-linked recessive

Y-linked

Correct Answer: D

Solution:

The trait is passed from father to son and is not seen in females, indicating a Y-linked inheritance pattern.

9:3:3:1

1:1:1:1

3:1

1:2:1

Correct Answer: B

Solution:

The cross RrYy x rryy is expected to produce a phenotypic ratio of 1:1:1:1 for round yellow, round green, wrinkled yellow, and wrinkled green seeds, respectively.

A cross between two heterozygous individuals

A cross between an individual with unknown genotype and a homozygous recessive individual

A cross between two homozygous dominant individuals

A cross between two homozygous recessive individuals

Correct Answer: B

Solution:

A test-cross is used to determine the genotype of an individual with a dominant phenotype by crossing it with a homozygous recessive individual.

Presence of an extra X chromosome

Absence of one X chromosome

Trisomy of chromosome 13

Trisomy of chromosome 21

Correct Answer: B

Solution:

Turner's syndrome is characterized by the absence of one X chromosome, leading to an XO configuration.

Deletion of a gene

Substitution of a single base pair in DNA

Insertion of an extra chromosome

Duplication of a gene

Correct Answer: B

Solution:

Sickle-cell anemia is caused by a point mutation, specifically the substitution of a single base pair in the gene coding for the beta-chain of hemoglobin.

3:1

9:3:3:1

1:1

1:2:1

Correct Answer: B

Solution:

The phenotypic ratio observed in a dihybrid cross according to Mendel's Law of Independent Assortment is 9:3:3:1.

Trisomy 21

Sickle-cell anemia

Klinefelter's syndrome

Turner's syndrome

Correct Answer: B

Solution:

Sickle-cell anemia is caused by a point mutation, which is a change of a single base pair in DNA.

Autosomal dominant

Autosomal recessive

X-linked dominant

X-linked recessive

Correct Answer: A

Solution:

The trait appearing in every generation and affecting both sexes equally suggests an autosomal dominant mode of inheritance.

A mutation in the gene coding for beta-globin

A lack of enzyme converting phenylalanine to tyrosine

An extra chromosome 21

A deletion in the alpha-globin gene

Correct Answer: B

Solution:

Phenylketonuria is caused by a lack of the enzyme that converts phenylalanine into tyrosine, leading to accumulation of phenylalanine.

Aneuploidy; Down's syndrome

Aneuploidy; Edwards syndrome

Polyploidy; Klinefelter's syndrome

Aneuploidy; Patau syndrome

Correct Answer: B

Solution:

The presence of an extra chromosome 22 is a form of aneuploidy, specifically known as Edwards syndrome, which is typically associated with trisomy 18, but the question hypothetically links it to chromosome 22.

3:1

9:3:3:1

1:1

1:2:1

Correct Answer: A

Solution:

Since the genes are linked and no recombination occurs, the phenotypic ratio will follow a 3:1 pattern typical of a monohybrid cross, as the linked genes will be inherited together.

The disorder appears in every generation.

The disorder skips generations and appears only when both parents are carriers.

The disorder is passed from father to all sons.

The disorder appears only in males.

Correct Answer: B

Solution:

In an autosomal recessive disorder, the trait can skip generations and typically appears only when both parents are carriers, as the disorder requires two copies of the recessive allele to be expressed.

Point mutation

Frame-shift mutation

Nonsense mutation

Silent mutation

Correct Answer: A

Solution:

The disorder is caused by a point mutation, which is a change in a single base pair in DNA, leading to the substitution of valine for glutamic acid in the beta-globin chain.

1/16

3/16

9/16

1/4

Correct Answer: B

Solution:

The cross RrYy x rryy results in offspring with the following genotypes: RrYy, Rryy, rrYy, and rryy. The round green phenotype (Rryy) occurs in 3 out of 16 offspring, giving a proportion of 3/16.

All offspring will have wild-type body color and normal wings.

All female offspring will have wild-type body color and normal wings, while male offspring will have white body color and normal wings.

All female offspring will have white body color and normal wings, while male offspring will have wild-type body color and normal wings.

All offspring will have white body color and normal wings.

Correct Answer: B

Solution:

The female offspring inherit the X+ from the father and Xw from the mother, resulting in wild-type body color (X+Xw) and normal wings (Ww). The male offspring inherit Xw from the mother and Y from the father, resulting in white body color (XwY) and normal wings (Ww).

Gregor Mendel

Thomas Hunt Morgan

Walter Sutton

Theodore Boveri

Correct Answer: A

Solution:

Gregor Mendel conducted hybridization experiments on garden peas and proposed the laws of inheritance.

9 colored : 3 no color : 3 no color : 1 no color

9 colored : 3 colored : 3 no color : 1 no color

12 colored : 4 no color

16 colored : 0 no color

Correct Answer: B

Solution:

In this scenario, the phenotypic expression of the flower color is dependent on two genes. The first gene (C/c) determines the potential for color, while the second gene (D/d) determines whether the color can be expressed. The cross between two heterozygous plants (CcDd x CcDd) will follow the dihybrid cross pattern. The phenotypic ratio can be determined by examining the independent assortment of the genes: 9 (C-D-) colored, 3 (C-dd) no color, 3 (ccD-) no color, 1 (ccdd) no color. Thus, the correct phenotypic ratio is 9 colored : 3 colored : 3 no color : 1 no color.

25%

50%

75%

Correct Answer: B

Solution:

If both parents are heterozygous (genotypes AO and BO), the possible genotypes for the offspring are AB, AO, BO, and OO. The probability of having blood group O (genotype OO) is 1 out of 4, or 25%.

Down's syndrome

Sickle-cell anemia

Turner's syndrome

Klinefelter's syndrome

Correct Answer: B

Solution:

Sickle-cell anemia is caused by a single base substitution in the gene coding for the beta-chain of hemoglobin, resulting in the replacement of glutamic acid with valine.

Genotype

Phenotype

Allele

Chromosome

Correct Answer: B

Solution:

The physical expression of a character is called the phenotype.

9:3:3:1

1:1:1:1

3:1

1:2:1

Correct Answer: A

Solution:

The expected phenotypic ratio for a dihybrid cross where both parents are heterozygous (RrBb x RrBb) and the loci are unlinked is 9:3:3:1. This is derived from the independent assortment of the two traits.

Down's syndrome

Klinefelter's syndrome

Turner's syndrome

Sickle-cell anemia

Correct Answer: C

Solution:

Turner's syndrome is characterized by a missing X chromosome in females.

The genes are unlinked and assort independently.

The genes are tightly linked and rarely recombine.

The genes are loosely linked and frequently recombine.

The genes are located on different chromosomes.

Correct Answer: B

Solution:

A recombination frequency of 1.5% indicates that the genes are tightly linked and recombine infrequently.

Round seed shape

Yellow seed color

Green pod color

Wrinkled seed shape

Correct Answer: D

Solution:

In Mendel's experiments, the wrinkled seed shape was a recessive trait.

It states that alleles segregate independently during gamete formation.

It describes the dominance of one allele over another.

It explains the blending of traits in offspring.

It refers to the mutation of genes during meiosis.

Correct Answer: A

Solution:

The Law of Independent Assortment states that alleles of different genes segregate independently of each other during gamete formation.

The traits are controlled by multiple alleles.

The traits are linked on the same chromosome.

The traits are sex-linked.

There is a mutation in the population.

Correct Answer: B

Solution:

The observation that certain traits do not follow the Law of Independent Assortment suggests that the genes controlling these traits are linked on the same chromosome.

Correct Answer: C

Solution:

A diploid organism heterozygous for four loci can produce 2^4 = 16 different types of gametes, as each locus can independently assort into two alleles.

All offspring will have wild-type eye color.

All male offspring will have the mutation, and all female offspring will have wild-type eye color.

All female offspring will have the mutation, and all male offspring will have wild-type eye color.

The mutation will not be expressed in any offspring.

Correct Answer: B

Solution:

Since the mutation is X-linked, male offspring receive their X chromosome from the mother and Y chromosome from the father, resulting in wild-type males. Female offspring receive one X chromosome from each parent, so they will be carriers if the mother is wild-type.

3:1

9:3:3:1

1:1

1:2:1

Correct Answer: B

Solution:

The phenotypic ratio observed in the F2 generation of a dihybrid cross is 9:3:3:1, according to Mendel's Law of Independent Assortment.

Increased efficiency of ATP production

Decreased efficiency of ATP production

No change in ATP production efficiency

Complete halt of ATP production

Correct Answer: B

Solution:

A point mutation that alters an amino acid in a protein involved in cellular respiration can lead to decreased efficiency of ATP production due to impaired protein function.

Correct Answer: C

Solution:

The number of different types of gametes is calculated as 2^n, where n is the number of heterozygous loci. For three loci, 2^3 = 8 different gametes can be produced.

Missense mutation

Nonsense mutation

Silent mutation

Frameshift mutation

Correct Answer: A

Solution:

A missense mutation results in the substitution of one amino acid for another in the protein product, potentially altering its function.

Down's syndrome

Turner's syndrome

Klinefelter's syndrome

Sickle-cell anemia

Correct Answer: A

Solution:

Down's syndrome is caused by trisomy of chromosome 21, resulting in an extra copy of this chromosome.

True or False

Correct Answer: True

Solution:

In humans, the normal female karyotype includes two X chromosomes (XX), and the male karyotype includes one X and one Y chromosome (XY).

Correct Answer: False

Solution:

Mendel's Law of Independent Assortment states that the segregation of one pair of characters is independent of another pair.

Correct Answer: True

Solution:

Sickle-cell anemia results from a single base substitution at the sixth codon of the beta globin gene, causing valine to replace glutamic acid.

Correct Answer: False

Solution:

Phenylketonuria is inherited as an autosomal recessive trait.

Correct Answer: False

Solution:

In humans, males have one X and one Y chromosome, which are not identical.

Correct Answer: True

Solution:

Sutton and Boveri united the knowledge of chromosomal segregation with Mendelian principles, forming the chromosomal theory of inheritance.

Correct Answer: False

Solution:

Thalassemia is an autosome-linked recessive blood disease caused by mutations or deletions affecting the synthesis of globin chains, not by chromosomal arrangement.

Correct Answer: False

Solution:

The chromosomal theory of inheritance was developed after Mendel's principles, integrating chromosomal behavior with Mendelian genetics.

Correct Answer: True

Solution:

Mendel's work was not widely recognized initially because communication was not as advanced, and his use of mathematics in biology was unconventional at the time.

Correct Answer: False

Solution:

Down's syndrome is caused by an extra copy of chromosome 21, not a missing chromosome.

Correct Answer: False

Solution:

A normal male has 22 pairs of autosomes and one pair of sex chromosomes.

Correct Answer: False

Solution:

Recessive traits are expressed only in a homozygous condition, not in a heterozygous condition.

Correct Answer: False

Solution:

Sickle-cell anemia is a qualitative problem of synthesizing an incorrectly functioning globin, not a quantitative problem.

Correct Answer: True

Solution:

Mendel's work was not recognized until 1900 due to several reasons, including the lack of communication and acceptance of his ideas at the time.

Correct Answer: False

Solution:

Down's syndrome is caused by trisomy of chromosome 21, resulting in a total of 47 chromosomes.

Correct Answer: True

Solution:

A normal human cell contains 46 chromosomes, which includes 22 pairs of autosomes and one pair of sex chromosomes.

Correct Answer: False

Solution:

Turner's syndrome is characterized by the absence of one X chromosome, resulting in a 45, XO karyotype.

Correct Answer: True

Solution:

Sickle-cell anemia is caused by a mutation that leads to the synthesis of incorrectly functioning hemoglobin molecules, which is a qualitative issue.

Correct Answer: False

Solution:

Turner's syndrome is actually caused by the absence of one X chromosome in females, resulting in an XO sex chromosome configuration.

Correct Answer: False

Solution:

Mendel's work remained unrecognized until 1900 due to various reasons, including the lack of communication and acceptance of his ideas.

Correct Answer: True

Solution:

Sickle-cell anemia results from a single base substitution in the beta globin gene, causing an amino acid change.

Correct Answer: True

Solution:

The 9:3:3:1 ratio observed in dihybrid crosses led to the formulation of the Law of Independent Assortment.

Correct Answer: True

Solution:

Morgan coined the term linkage to describe the physical association of genes on a chromosome.

Correct Answer: True

Solution:

Humans have a total of 46 chromosomes, which includes 22 pairs of autosomes and one pair of sex chromosomes.

Correct Answer: False

Solution:

Genes located on the same chromosome tend to be inherited together and do not always show independent assortment. This phenomenon is known as linkage.

Correct Answer: False

Solution:

Thalassemia is a quantitative problem of synthesizing too few globin molecules.

Correct Answer: True

Solution:

The Punnett square is a tool used to illustrate the independent segregation of genes during meiosis, showing the possible combinations of alleles in gametes.

Correct Answer: False

Solution:

In humans, a normal male has 22 pairs of autosomes and a pair of sex chromosomes as XY.

Correct Answer: True

Solution:

Down's syndrome results from trisomy of chromosome 21, leading to a total of 47 chromosomes.

Correct Answer: False

Solution:

Down's syndrome is caused by trisomy of chromosome 21, which is an example of aneuploidy, not polyploidy.

Correct Answer: False

Solution:

The chromosomal theory of inheritance was proposed by Sutton and Boveri, not rediscovered by de Vries, Correns, and von Tschermak. The latter rediscovered Mendel's work on inheritance.

Correct Answer: True

Solution:

Mendel applied statistical analysis and mathematical logic to his experiments on inheritance.

Correct Answer: True

Solution:

Sutton and Boveri united the knowledge of chromosomal segregation with Mendelian principles to propose the chromosomal theory of inheritance.

Correct Answer: True

Solution:

Walter Sutton and Theodore Boveri noted that the behavior of chromosomes during meiosis paralleled the behavior of Mendel's 'factors' (genes), leading to the formulation of the chromosomal theory of inheritance. This theory connected the segregation and independent assortment of chromosomes to Mendel's laws, providing a physical basis for inheritance patterns.

Correct Answer: False

Solution:

The Law of Independent Assortment states that the segregation of one pair of characters is independent of the other pair.

Principles of Inheritance and Variation

AI Learning Assistant

CBSE Learning Objectives – Key Concepts & Skills You Must Know

Learning Objectives

CBSE Revision Notes & Quick Summary for Last-Minute Study

Chapter 4: Principles of Inheritance and Variation

Overview

Key Concepts

Mendel's Laws of Inheritance

Genetic Terms

Genetic Disorders

Mutation

Pedigree Analysis

Polygenic Inheritance

Pleiotropy

Sex Determination

CBSE Exam Tips, Important Questions & Common Mistakes to Avoid

Common Mistakes and Exam Tips

Common Pitfalls

Tips for Exam Preparation

Multiple Choice Questions

Q1.In Mendel's experiments, which trait was dominant for seed shape?

Correct Answer: A

Q2.What is the chromosomal composition of a normal human male?

Correct Answer: B

Q3.A couple has a child with blood group O. If the father has blood group A and the mother has blood group B, what are the possible genotypes of the parents?

Correct Answer: B

Q4.Consider a situation where a geneticist is studying a dihybrid cross in Drosophila. The genes for body color and wing shape are on the same chromosome but are separated by a large distance. What is the most likely outcome regarding the recombination frequency?

Correct Answer: B

Q5.Which of the following describes a point mutation?

Correct Answer: B

Q6.What is the chromosomal composition of a normal human female?

Correct Answer: B

Q7.A biologist is studying the inheritance of two traits in a plant species: leaf color and stem height. If the biologist observes a 9:3:3:1 phenotypic ratio in the F2 generation, what does this indicate about the genes controlling these traits?

Correct Answer: B

Q8.What is the chromosomal basis for Down's syndrome?

Correct Answer: A

Q9.In Mendel's experiments, which of the following traits was considered dominant for seed color?

Correct Answer: B

Correct Answer: C

Q11.Which scientist is credited with the experimental verification of the chromosomal theory of inheritance?

Correct Answer: B

Q12.In a study of chromosomal disorders, a scientist finds a human cell with 47 chromosomes. Which of the following conditions could this cell represent?

Correct Answer: C

Q13.In a genetic experiment, a researcher observes that a certain trait in a plant species follows the pattern of incomplete dominance. If a homozygous red-flowered plant is crossed with a homozygous white-flowered plant, what would be the expected phenotype of the F1 generation?

Correct Answer: C

Q14.A certain genetic disorder is caused by a point mutation in a gene located on chromosome 11. If this disorder follows an autosomal recessive pattern, what is the probability that two carrier parents will have an affected child?

Correct Answer: A

Q15.A researcher is studying a pedigree chart for a family with a history of an autosomal recessive disorder. If both parents are carriers of the disorder, what is the probability that their child will be affected?

Correct Answer: A

Q16.In a hypothetical experiment, a geneticist crosses two pea plants, one with genotype RrYy and another with genotype RrYY. Assuming independent assortment, what is the expected phenotypic ratio of the offspring?

Correct Answer: A

Correct Answer: A

Q18.A scientist observes a chromosomal disorder in a plant species where the total number of chromosomes is increased by one. What is this condition called?

Correct Answer: B

Q19.Which scientist is known for using fruit flies to study genetic inheritance?

Correct Answer: B

Q20.In a genetic experiment, two heterozygous plants (TtYy) are crossed. If the genes for tallness (T) and yellow seeds (Y) are linked, what is the expected phenotypic ratio of the offspring assuming no recombination occurs?

Correct Answer: C

Q21.A geneticist is studying a rare genetic disorder caused by a point mutation. Which of the following best describes a point mutation?

Correct Answer: B

Q22.In a hypothetical experiment, a biologist crosses two plants with genotypes AaBb and AaBb. If the two loci are linked and show a recombination frequency of 20%, what is the expected phenotypic ratio in the offspring?

Correct Answer: C

Q23.A geneticist is analyzing a pedigree chart and notices that a certain trait is passed from father to son and is not seen in females. Which type of inheritance pattern does this suggest?

Correct Answer: D

Q24.In a dihybrid cross involving two traits, seed shape and seed color, a plant with round yellow seeds (RrYy) is crossed with a plant with wrinkled green seeds (rryy). What is the expected phenotypic ratio of the offspring?

Correct Answer: B

Q25.Which of the following best describes a test-cross?

Correct Answer: B

Q26.Which of the following is a characteristic of Turner's syndrome?

Correct Answer: B

Q27.What is the primary cause of sickle-cell anemia?

Correct Answer: B

Q28.What is the phenotypic ratio observed in a dihybrid cross according to Mendel's Law of Independent Assortment?

Correct Answer: B

Q29.Which of the following is an example of a point mutation?

Correct Answer: B

Q30.In a pedigree analysis, a geneticist observes that a certain trait appears in every generation and affects both males and females equally. What is the most likely mode of inheritance for this trait?

Correct Answer: A

Q31.What is the main cause of phenylketonuria?