Q: A population of 400 individuals has the following genotype counts for a gene with two alleles (A and a): $$N_{AA} = 90$$, $$N_{Aa} = 40$$, $$N_{aa} = 70. $$What is the frequency of allele A in this population?

$$p = \frac{2N_{AA} + N_{Aa}}{2N} = \frac{2 \times 90 + 40}{2 \times 200} = \frac{220}{400} = 0.55$$

Q: If a population is in Hardy-Weinberg equilibrium and the frequency of allele A is $$p = 0.7$$, what is the expected frequency of heterozygotes (Aa)?

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

Q: In a population of 1000 individuals, you observe 220 AA, 500 AC, and 280 CC genotypes. What is the expected number of AC individuals under Hardy-Weinberg equilibrium if $$p = 0.473$$ and $$q = 0.527$$?

$$2pq \times 1000 = 2 \times 0.473 \times 0.527 \times 1000 = 0.499 \times 1000 = 499$$

Question 1

Which of the following best describes the Hardy-Weinberg equilibrium?

Accepted Answer

A state in which allele and genotype frequencies remain constant from generation to generation in the absence of evolutionary influences.

Question 2

A population of 400 individuals has the following genotype counts for a gene with two alleles (A and a): $$N_{AA} = 90$$, $$N_{Aa} = 40$$, $$N_{aa} = 70. $$What is the frequency of allele A in this population?

Accepted Answer

$$p = \frac{2N_{AA} + N_{Aa}}{2N} = \frac{2 	imes 90 + 40}{2 	imes 200} = \frac{220}{400} = 0.55$$

Question 3

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

Accepted Answer

Small population size

Question 4

If a population is in Hardy-Weinberg equilibrium and the frequency of allele A is $$p = 0.7$$, what is the expected frequency of heterozygotes (Aa)?

Accepted Answer

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

Question 5

Which evolutionary process is correctly matched with its effect on allele frequencies?

Accepted Answer

Gene flow: introduces or removes alleles from a population by migration

Question 6

A population of butterflies has the following genotype frequencies for a gene with two alleles (A and C): $$f(AA) = 0.369$$, $$f(AC) = 0.208$$, $$f(CC) = 0.423. $$What is the observed frequency of allele A?

Accepted Answer

$$f(A) = f(AA) + \frac{1}{2}f(AC) = 0.369 + 0.104 = 0.473$$

Question 7

Which scenario would most likely cause a population to deviate from Hardy-Weinberg equilibrium?

Accepted Answer

A small group of individuals migrates into the population, introducing new alleles.

Question 8

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

Accepted Answer

It describes a situation where no evolutionary processes are acting, so any deviation from its predictions indicates evolution is occurring.

Question 9

In a population of 1000 individuals, you observe 220 AA, 500 AC, and 280 CC genotypes. What is the expected number of AC individuals under Hardy-Weinberg equilibrium if $$p = 0.473$$ and $$q = 0.527$$?

Accepted Answer

$$2pq 	imes 1000 = 2 	imes 0.473 	imes 0.527 	imes 1000 = 0.499 	imes 1000 = 499$$

Question 10

Which of the following statements about genetic drift is correct?

Accepted Answer

It causes random changes in allele frequencies, especially in small populations.

Question 11

A population is found to have genotype frequencies that do not match Hardy-Weinberg expectations. What is the most reasonable conclusion?

Accepted Answer

At least one of the Hardy-Weinberg assumptions is being violated, and evolution may be occurring.

Question 12

If a population is monomorphic at a locus, what does this mean?

Accepted Answer

There is only one allele at that locus, and its frequency is 1.

Question 13

Which of the following is a real-world application of the Hardy-Weinberg principle?

Accepted Answer

Testing whether a gene in a population is evolving by comparing observed and expected genotype frequencies.

Question 14

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

Accepted Answer

Mutation

Question 15

A population has allele frequencies $$p = 0.4$$ and $$q = 0.6. $$What is the expected frequency of the homozygous recessive genotype under Hardy-Weinberg equilibrium?

Accepted Answer

$$q^2$$ = $$(0.6)^2 = 0.36$

Question 16

Which of the following best explains why populations in nature rarely meet all Hardy-Weinberg assumptions?

Accepted Answer

Evolutionary processes such as selection, drift, gene flow, and mutation are almost always acting to change allele frequencies.

Question 17

In a case study, researchers hypothesize that a butterfly gene is under strong selection. What result would support this hypothesis?

Accepted Answer

Observed genotype frequencies significantly differ from Hardy-Weinberg expectations for that gene.

Question 18

Which formula correctly represents the Hardy-Weinberg equation for a gene with two alleles?

Accepted Answer

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

Question 19

If a population is in Hardy-Weinberg equilibrium, what will happen to allele and genotype frequencies over generations?

Accepted Answer

They will remain constant from generation to generation.

Question 20

Which of the following is an example of gene flow?

Accepted Answer

Wolves from one pack migrate and breed with wolves from another pack, introducing new alleles.

Chapter 23: Evolutionary Processes and the Hardy-Weinberg Principle

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