Q: A population of 1,000 individuals has the following genotype frequencies for a gene with two alleles, A and a: 490 AA, 420 Aa, and 90 aa. What is the frequency of the a allele?

$$f(a) = \frac{2 \times 90 + 420}{2 \times 1000} = \frac{180 + 420}{2000} = \frac{600}{2000} = 0.3$$

Q: In a population, the observed genotype frequencies for a gene are: AA = 0.36, Aa = 0.48, aa = 0.16. What are the allele frequencies for A and a?

$$f(A) = 0.36 + 0.5 \times 0.48 = 0.36 + 0.24 = 0.60$$, $$f(a) = 0.16 + 0.24 = 0.40$$

Q: In Hardy-Weinberg equilibrium, what is the expected frequency of heterozygotes for a gene with allele frequencies $$p = 0.7$$ and $$q = 0.3$$?

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

Question 1

Which of the following is NOT an assumption of the Hardy-Weinberg equilibrium?

Accepted Answer

Genotypes have unequal fitness

Question 2

A population of 1,000 individuals has the following genotype frequencies for a gene with two alleles, A and a: 490 AA, 420 Aa, and 90 aa. What is the frequency of the a allele?

Accepted Answer

$$f(a) = \frac{2 	imes 90 + 420}{2 	imes 1000} = \frac{180 + 420}{2000} = \frac{600}{2000} = 0.3$$

Question 3

Which evolutionary process is most likely responsible for a drastic reduction in genetic diversity following a natural disaster that kills most of a population?

Accepted Answer

Genetic drift (bottleneck effect)

Question 4

In a population, the frequency of a recessive genetic disease is 1 in 10,000. Assuming Hardy-Weinberg equilibrium, what is the approximate frequency of carriers (heterozygotes)?

Accepted Answer

$$q^2$$ = \frac{1}{10,000} = 0.0001$$, q$$ = \sqrt{0.0001} = 0.01$$, p = 1 - 0.01 = 0.99$, carriers = 2pq = 2$$ 	imes 0.99 	imes 0.01 = 0.0198$$

Question 5

Which of the following best describes the effect of heterozygote advantage on allele frequencies in a population?

Accepted Answer

It maintains both alleles at higher frequencies than expected under Hardy-Weinberg equilibrium

Question 6

A population of plants has 2,000 yellow-seeded (YY or Yy) and 500 green-seeded (yy) individuals. Yellow is dominant to green. What is the frequency of the y allele?

Accepted Answer

$$q^2$$ = \frac{500}{2500} = 0.2$$, q$$ = \sqrt{0.2} \approx 0.447$$

Question 7

Which statement about microsatellites (STRs) is TRUE?

Accepted Answer

They are short tandem repeats used to study genetic variation

Question 8

If a population is NOT in Hardy-Weinberg equilibrium, which of the following could be a possible explanation?

Accepted Answer

Genetic drift

Question 9

In a population, the observed genotype frequencies for a gene are: AA = 0.36, Aa = 0.48, aa = 0.16. What are the allele frequencies for A and a?

Accepted Answer

$$f(A) = 0.36 + 0.5 	imes 0.48 = 0.36 + 0.24 = 0.60$$, $$f(a) = 0.16 + 0.24 = 0.40$$

Question 10

Which of the following is an example of gene flow in a population?

Accepted Answer

Individuals migrate into a population, bringing new alleles

Question 11

A rare X-linked recessive condition is present in 12% of males in a population. What is the expected frequency of affected females?

Accepted Answer

$$q^2$$ = $$(0.12)^2 = 0.0144$

Question 12

Which of the following best describes the founder effect?

Accepted Answer

A small group of individuals establishes a new population, leading to reduced genetic diversity

Question 13

In Hardy-Weinberg equilibrium, what is the expected frequency of heterozygotes for a gene with allele frequencies $$p = 0.7$$ and $$q = 0.3$$?

Accepted Answer

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

Question 14

Which process is the ultimate source of all genetic variation in a population?

Accepted Answer

Mutation

Question 15

A population of 500 individuals has the following genotype frequencies for a gene: MM = 0.298, MN = 0.489, NN = 0.213. What is the frequency of the N allele?

Accepted Answer

$$f(N) = 0.213 + 0.5 	imes 0.489 = 0.213 + 0.2445 = 0.4575$$

Question 16

Which of the following would violate the assumption of random mating in Hardy-Weinberg equilibrium?

Accepted Answer

Individuals mate preferentially with relatives

Question 17

If the observed and expected genotype frequencies in a population do NOT match, what does this indicate?

Accepted Answer

There may be evolutionary forces acting on the population

Question 18

Which of the following is NOT a requirement for natural selection to occur?

Accepted Answer

All genotypes have equal fitness

Question 19

A population is in Hardy-Weinberg equilibrium for a gene with two alleles, A and a. If the frequency of allele A is 0.8, what is the expected frequency of genotype aa?

Accepted Answer

$$q = 1 - 0.8 = 0.2$$, $$q^2$$ = $$(0.2)^2 = 0.04$

Population Genetics: Principles, Calculations, and Evolutionary Processes

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