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 the a allele ($$q) in $$this population?

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

Q: A population of butterflies has two alleles for wing color: B (black) and b (white). If $$p = 0.7$$ and $$q = 0.3$$, what is the expected frequency of heterozygotes ($$Bb) $$under Hardy-Weinberg equilibrium?

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

Question 1

Which of the following best describes the difference between allele frequency and genotype frequency in a population?

Accepted Answer

Allele frequency is the proportion of a specific allele among all alleles at a locus, while genotype frequency is the proportion of a specific genotype among all individuals in the population.

Question 2

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 the a allele ($$q) in $$this population?

Accepted Answer

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

Question 3

Which of the following is NOT a condition required for a population to remain in Hardy-Weinberg equilibrium?

Accepted Answer

Small population size

Question 4

If a population is in Hardy-Weinberg equilibrium, what does this indicate about the population?

Accepted Answer

Allele and genotype frequencies remain constant from generation to generation.

Question 5

A population of butterflies has two alleles for wing color: B (black) and b (white). If $$p = 0.7$$ and $$q = 0.3$$, what is the expected frequency of heterozygotes ($$Bb) $$under Hardy-Weinberg equilibrium?

Accepted Answer

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

Question 6

Which of the following scenarios best illustrates the founder effect?

Accepted Answer

A small group of individuals colonizes a new island, carrying only a subset of the genetic variation from the original population.

Question 7

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

Accepted Answer

$$p + q = 1$$

Question 8

A population of plants is exposed to a new herbicide. Over several generations, only plants with a rare allele survive and reproduce. Which type of selection is most likely occurring?

Accepted Answer

Directional selection

Question 9

Why is the Hardy-Weinberg equilibrium considered a null hypothesis in evolutionary biology?

Accepted Answer

It provides a baseline expectation for allele and genotype frequencies in the absence of evolutionary forces.

Question 10

Which of the following best explains why genetic drift has a greater effect on small populations?

Accepted Answer

Random changes in allele frequencies are more likely to lead to fixation or loss of alleles in small populations.

Question 11

A population of 500 individuals is in Hardy-Weinberg equilibrium for a gene with two alleles, M and m. If the frequency of the mm genotype is 0.16, what is the frequency of the M allele ($$p$$)?

Accepted Answer

$$q^2 = 0.16$$ \Rightarrow q = 0.4; p = 1 - 0.4 = 0.6$$

Question 12

Which of the following is an example of a detrimental allele being maintained in a population due to evolutionary forces?

Accepted Answer

The sickle-cell allele persists in populations where malaria is common because heterozygotes have increased resistance to malaria.

Question 13

Which of the following best describes stabilizing selection?

Accepted Answer

It favors intermediate phenotypes and reduces variation.

Question 14

If a mutation occurs in the intron region of a gene, what is the most likely outcome?

Accepted Answer

It may have no effect on the phenotype since introns are non-coding regions.

Question 15

Which process introduces new alleles into a population's gene pool?

Accepted Answer

Mutation

Question 16

A population of birds is split by a natural disaster, and only a few survive. Over time, the new population shows much less genetic variation than the original. This is an example of:

Accepted Answer

Bottleneck effect

Question 17

Why can't natural selection create perfect organisms?

Accepted Answer

Natural selection can only act on existing variation and is limited by historical constraints and trade-offs.

Question 18

Which of the following would violate the Hardy-Weinberg equilibrium in a population?

Accepted Answer

Natural selection favoring a particular genotype

Question 19

If $$p = 0.8$$ and $$q = 0.2 in a $$population, what is the expected frequency of the homozygous recessive genotype under Hardy-Weinberg equilibrium?

Accepted Answer

$$q^2$$ = $$0.2^2 = 0.04$

Question 20

Which of the following best describes disruptive selection?

Accepted Answer

It favors individuals at both extremes of a phenotypic range.

Population Genetics and Evolution: Hardy-Weinberg and Genetic Variation

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