Hardy-Weinberg Quiz

1. If the frequency of two alleles in a gene pool is 90% A and 10% a, what is the frequency of individuals in the population with the genotype Aa?

a) .81 b) .09 c) .18 d) .01 e) .198

Correct! The question tells you that p = 0.9 and q = 0.1. From this, you can calculate the heterozygotes: 2pq = 2 (0.9) (0.1) = 0.18. If you selected e as your response, you may have confused the allelic frequency with genotypic frequency. This problem gives you the allelic frequency of a, which is 10%. To review the difference betwen allelic frequency and genomic frequency, return to Allelic Frequency vs Genotypic Frequency.

2. If a population experiences no migration, is very large, has no mutations, has random mating, and there is no selection, which of the following would you predict?

a) The population will evolve, but much more slowly than normal.
b) The makeup of the population's gene pool will remain virtually the same as long as these conditions hold.
c) The composition of the population's gene pool will change slowly in a predictable manner.
d) Dominant alleles in the population's gene pool will slowly increase in frequency while recessive alleles will decrease.
e) The population probably has an equal frequency of A and a alleles.

Correct! The conditions described all contribute to genetic equilibrium, where it would be expected for initial gene frequencies to remain constant generation after generation. If you chose e, remember that genetic equilibrium does not mean that the frequency of A = the frequency of a.

3. Which of the following is NOT a condition that must be met for Hardy-Weinberg equilibrium?

a) Large population size
b) No mutations
c) No immigration or emigration
d) Dominant alleles more frequent than recessive alleles
e) No natural selection

Correct! Like question 2, this question is intended to emphasize the point that the initial frequency of alleles has nothing to do with genetic equilibrium.

4. In a population that is in Hardy-Weinberg equilibrium, the frequency of the homozygous recessive genotype is 0.09. What is the frequency of individuals that are homozygous for the dominant allele?

a) 0.7 b) .21 c) .42 d) .49 e) .91

Correct! The correct answer is d. q² = 0.09, so q = 0.3.
p = 1 - q, so p = 1 - 0.3 = 0.7
AA = q² = 0.49

5. In humans, Rh-positive individuals have the Rh antigen on their red blood cells, while Rh-negative individuals do not. If the Rh-positive phenotype is produced by a dominant gene (A), and the Rh-negative phenotype is due to its recessive allele (a), what is the frequency of the Rh-positive allele if 84% of a population is Rh-positive?

a) .04 b) .16 c) .48 d) .60 e) .84

Correct! The correct answer is d. q² = 0.16; q = 0.4
p = 1 - q, so p = 0.6 = 60%