Q: A population of butterflies has two alleles for a gene: A and C. If the frequency of A is 0.6 and the frequency of C is 0.4, what is the expected frequency of heterozygotes (AC) under Hardy–Weinberg equilibrium?

$2pq = 2 \times 0.6 \times 0.4 = 0.48$

Question 1

Which of the following best describes the Hardy–Weinberg equilibrium for a gene with two alleles, A and a, with frequencies $p$ and $q$ in a large, randomly mating population?

Accepted Answer

Genotype frequencies are given by $p^2$ for AA, $2pq$ for Aa, and $q^2$ for aa, and allele frequencies remain constant.

Question 2

A population of butterflies has two alleles for a gene: A and C. If the frequency of A is 0.6 and the frequency of C is 0.4, what is the expected frequency of heterozygotes (AC) under Hardy–Weinberg equilibrium?

Accepted Answer

$2pq = 2 	imes 0.6 	imes 0.4 = 0.48$

Question 3

Which of the following is NOT an assumption of the Hardy–Weinberg principle?

Accepted Answer

Natural selection is acting on the population.

Question 4

In a small population of fruit flies, one allele is lost after several generations. This is most likely due to which evolutionary process?

Accepted Answer

Genetic drift

Question 5

Which mode of natural selection increases genetic variation by favoring extreme phenotypes at both ends of the range?

Accepted Answer

Disruptive selection

Question 6

A population bottleneck can lead to which of the following outcomes?

Accepted Answer

Random loss of alleles and reduced genetic variation

Question 7

Which of the following statements about inbreeding is correct?

Accepted Answer

Inbreeding increases homozygosity and can lead to inbreeding depression.

Question 8

Which evolutionary process is the ultimate source of new alleles in a population?

Accepted Answer

Mutation

Question 9

In a population of steelhead trout, gene flow from captive-bred to wild populations resulted in which of the following outcomes?

Accepted Answer

Decreased fitness of wild populations

Question 10

Which of the following best describes balancing selection?

Accepted Answer

It maintains genetic variation by favoring heterozygotes or rare alleles.

Question 11

A population of birds colonizes a new island. The allele frequencies in the new population differ from the source population. This is an example of:

Accepted Answer

Founder effect

Question 12

Which of the following is true about mutation as an evolutionary process?

Accepted Answer

Mutation is random with respect to fitness and most mutations are deleterious.

Question 13

Which equation represents the sum of allele frequencies for a gene with two alleles in a population?

Accepted Answer

$p + q = 1$

Question 14

Which of the following is a real-world example of stabilizing selection?

Accepted Answer

Survival of human babies with average birth weight

Question 15

Which process always tends to reduce genetic differences between populations?

Accepted Answer

Gene flow

Question 16

If a population is not in Hardy–Weinberg equilibrium for a particular gene, what does this indicate?

Accepted Answer

One or more Hardy–Weinberg assumptions are being violated.

Question 17

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

Accepted Answer

A change in a single base pair in DNA

Question 18

Which evolutionary process is most likely to cause a loss of fitness in a population due to the random loss of alleles?

Accepted Answer

Genetic drift

Question 19

Which of the following is a consequence of inbreeding depression in small populations?

Accepted Answer

Higher mortality rates among offspring

Question 20

Which of the following best explains why mutation is considered the ultimate source of genetic variation?

Accepted Answer

Mutation creates entirely new alleles that did not previously exist in the population.

Chapter 23: Evolutionary Processes – Structured Study Notes

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