Q: A population is in Hardy-Weinberg equilibrium for a gene with two alleles, $$A$$ and $$a. If $$the frequency of allele $$A is$$ $$0.7$$, what is the expected frequency of heterozygotes?

$$2pq = 2 \times 0.7 \times 0.3 = 0.42$$

Question 1

Which of the following best explains the Chromosome Theory of Heredity as proposed by Sutton and Boveri?

Accepted Answer

Genes are located on chromosomes, and it is the chromosomes that segregate and independently assort during meiosis.

Question 2

A woman who is heterozygous for a sex-linked recessive disorder (such as hemophilia) marries a man who does not have the disorder. What is the probability that their son will have the disorder?

Accepted Answer

$$\frac{1}{2}$$

Question 3

Which of the following is an example of pleiotropy?

Accepted Answer

A single gene mutation causing both sickle-shaped red blood cells and increased resistance to malaria.

Question 4

In a dihybrid cross involving two genes on the same chromosome, the observed offspring ratios deviate from the expected 9:3:3:1 ratio. What is the most likely explanation?

Accepted Answer

The genes are linked and do not assort independently.

Question 5

Which equation represents the Hardy-Weinberg equilibrium for a gene with two alleles, $$A$$ and $$a$$, with frequencies $$p$$ and $$q$$ respectively?

Accepted Answer

$$p^2 + 2pq$$ + $$q^2 = 1$

Question 6

A population of 1000 individuals has 360 individuals with genotype $$AA$$, 480 with $$Aa$$, and 160 with $$aa. $$What is the frequency of allele $$a$$?

Accepted Answer

$$0.4$$

Question 7

Which of the following best describes epistasis?

Accepted Answer

One gene masks or modifies the expression of another gene at a different locus.

Question 8

A geneticist is mapping three genes on a chromosome. The recombination frequencies are as follows: $$A$$-$$B is 10$$%, $$B$$-$$C is 5$$%, and $$A$$-$$C is 15$$%. What is the most likely gene order?

Accepted Answer

$$A$$-$$B$$-$$C$$

Question 9

Which of the following is a real-world example of cytoplasmic (maternal) inheritance?

Accepted Answer

Mitochondrial diseases passed from mother to all her children.

Question 10

A plant breeder uses marker-assisted selection to improve rice yield. Which of the following best describes this process?

Accepted Answer

Using molecular markers linked to desirable traits to select plants for breeding.

Question 11

Which of the following factors does NOT disrupt Hardy-Weinberg equilibrium in a population?

Accepted Answer

Random mating

Question 12

A pedigree shows a trait that appears in every generation and affects both males and females equally. What is the most likely mode of inheritance?

Accepted Answer

Autosomal dominant

Question 13

Which of the following best describes the concept of heritability in quantitative genetics?

Accepted Answer

The proportion of phenotypic variance in a population that is attributable to genetic variance.

Question 14

A genetic counselor is analyzing a pedigree for cystic fibrosis, an autosomal recessive disorder. If both parents are carriers, what is the probability that their child will be affected?

Accepted Answer

$$\frac{1}{4}$$

Question 15

Which of the following is a key application of gene therapy in medicine?

Accepted Answer

Treating genetic disorders such as muscular dystrophy by introducing functional copies of the gene.

Question 16

In a test cross, a plant with genotype $$AaBb is $$crossed with $$aabb. If $$the genes are unlinked, what is the expected phenotypic ratio among the offspring?

Accepted Answer

1:1:1:1

Question 17

Which of the following best explains the significance of crossing over during meiosis?

Accepted Answer

It increases genetic variation by exchanging genetic material between homologous chromosomes.

Question 18

A population is in Hardy-Weinberg equilibrium for a gene with two alleles, $$A$$ and $$a. If $$the frequency of allele $$A is$$ $$0.7$$, what is the expected frequency of heterozygotes?

Accepted Answer

$$2pq = 2 	imes 0.7 	imes 0.3 = 0.42$$

Question 19

Which of the following is an example of a modifier gene?

Accepted Answer

A gene that alters the expression of another gene, such as a gene that changes the severity of sickle cell anemia.

Question 20

A researcher uses a chi-square test to analyze the results of a genetic cross. Which of the following best describes the purpose of this test?

Accepted Answer

To determine whether the observed results differ significantly from the expected Mendelian ratios.

Principles and Applications of Genetics: Study Notes

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