Q: A population of 1000 individuals has the following genotype counts for a gene with two alleles (A and a): 490 AA, 420 Aa, and 90 aa. What is the frequency of allele a?

$$q = \frac{2 \times 90 + 420}{2 \times 1000} = 0.3$$

Question 1

Which of the following best describes epistasis in the context of gene-gene interactions?

Accepted Answer

A phenomenon where the expression of one gene is masked or modified by one or more other genes.

Question 2

A dihybrid cross between two heterozygotes for genes A and B produces a 9:7 phenotypic ratio in the offspring. What is the most likely explanation for this ratio?

Accepted Answer

Duplicate recessive epistasis, where both genes are required for the dominant phenotype.

Question 3

Which equation would you use to calculate the expected genotype frequencies under Hardy-Weinberg equilibrium for a gene with two alleles, A and a, with allele frequencies $$p$$ and $$q$$?

Accepted Answer

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

Question 4

A geneticist observes that two genes are inherited together more often than expected by chance. What is the most likely explanation?

Accepted Answer

The genes are linked and located close together on the same chromosome.

Question 5

In a test cross, the recombination frequency between two genes is found to be 12%. What is the approximate map distance between these genes?

Accepted Answer

12 centimorgans

Question 6

Which of the following best explains why crossing over during meiosis increases genetic diversity?

Accepted Answer

It allows for the exchange of genetic material between homologous chromosomes, creating new allele combinations.

Question 7

A population of 1000 individuals has the following genotype counts for a gene with two alleles (A and a): 490 AA, 420 Aa, and 90 aa. What is the frequency of allele a?

Accepted Answer

$$q = \frac{2 	imes 90 + 420}{2 	imes 1000} = 0.3$$

Question 8

Which of the following is a key assumption of the Hardy-Weinberg equilibrium?

Accepted Answer

Mating is random within the population.

Question 9

A researcher is using a chi-square test to compare observed and expected genotype frequencies. Which formula should they use?

Accepted Answer

$$\$$chi^2$$ = \sum \frac{(O - E)^2$}{E}$$

Question 10

Which of the following scenarios best illustrates positive selection in a population?

Accepted Answer

A rare allele increases in frequency because it confers resistance to a new disease.

Question 11

In a bacterial transformation experiment, which of the following is required for a recipient cell to acquire new genetic material?

Accepted Answer

Uptake of free DNA from the environment.

Question 12

Which of the following best describes the function of a conjugative plasmid in bacteria?

Accepted Answer

It enables the transfer of genetic material between bacteria via conjugation.

Question 13

A couple, both heterozygous for a recessive genetic disorder, are planning to have a child. What is the probability that their child will be affected by the disorder?

Accepted Answer

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

Question 14

Which of the following is an example of balancing selection?

Accepted Answer

Heterozygotes for sickle cell anemia have a survival advantage in malaria-endemic regions.

Question 15

Which of the following best explains why inbreeding increases the risk of genetic disorders?

Accepted Answer

It increases the probability that offspring will inherit two copies of a deleterious recessive allele.

Question 16

A mutation in the coding region of a gene results in a premature stop codon. What is the most likely phenotypic outcome?

Accepted Answer

The protein is truncated and likely nonfunctional.

Question 17

Which of the following best describes the process of transduction in bacteria?

Accepted Answer

Transfer of DNA from one bacterium to another via a bacteriophage.

Question 18

In a population, the frequency of allele A is 0.7 and allele a is 0.3. What is the expected frequency of heterozygotes under Hardy-Weinberg equilibrium?

Accepted Answer

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

Question 19

Which of the following is a real-world example of gene linkage affecting inheritance patterns?

Accepted Answer

The inheritance of red hair and freckles, which are often inherited together because the genes are close on the same chromosome.

Question 20

Which of the following best explains why certain phenotypes only appear under specific growth conditions in bacteria?

Accepted Answer

Some phenotypes require specific nutrients or conditions to be expressed.

Comprehensive Study Guide: Genetics Exam II

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