Name: _______________________________________
Hardy – Weinberg Equilibrium Practice Problems
SHOW YOUR WORK!
1. A population of hamsters has a gene consisting of 90% M alleles (black) and 10% m alleles (gray). Assuming
that the population is in H-W equilibrium, determine the proportion of offspring that will be black and the
proportion that will be gray.
2. In a certain population of 1000 fruit flies, 640 have red eyes while the remainder have sepia eyes. The sepia
eye trait is recessive to red eyes. Assuming that the population is in H-W equilibrium, how many individuals
would you expect to be homozygous for red eye color?
3. A type of deformity appears in 4% of large herd of cattle. Assume the deformity was caused by a recessive
allele. Assuming that the population is in H-W equilibrium, what is the frequency of the dominant allele? What
percentage of the herd are carriers of the gene?
4. Phenylketonuria (PKU) is a human metabolic disorder that results in mental retardation if it is untreated in
infancy. In the United States, one out of approximately 10,000 babies is born with the disorder. Assuming that
the population is in H-W equilibrium, approximately what percent of the population are heterozygous carriers of
the recessive PKU allele?
5. In humans, the ability to taste the chemical phenylthiocarbamide (PTC) is inherited as a simple dominant
characteristic. Suppose you found out that 360 out of 1000 college students could NOT taste the chemical.
Assuming that the population is in H-W equilibrium, determine the number of heterozygous students in this
population. Determine the number of students that are homozygous dominant in this population.
6. A moth's color is controlled by two alleles, G and g, at a single locus. G (gray) is dominant to g (white). A
large population of moths was studied, and the frequency of the G allele in the population over time was
documented, as shown in the figure below. In 1980, a random sample of 2,000 pupae was collected and moths
were allowed to emerge.
a. During which of the following time periods could the population have been in Hardy-Weinberg equilibrium
for the G locus?
I. 1960-1964
II. 1965-1972
III. 1973-1980
(A) I only
(B)
(C) III only
(D)
(E) I, II, and III
II only
I and III only
b. Assuming that the population was in Hardy-Weinberg equilibrium for the G locus, what percentage of moths
in the natural population was white in 1962?
(A) 2%
(B) 4%
(C) 8%
(D) 20%
(E) 64%
c. Assuming that the population was in Hardy-Weinberg equilibrium for the G locus, what percentage of the
gray moths that emerged in 1980 were heterozygous?
(A) 0%
(B) 25%
(C) 33%
(D) 67%
(E) 100%
d. Assuming that the population was in Hardy-Weinberg equilibrium for the G locus, what was the frequency of
allele G in the gray moths that emerged in 1980?
(A) 0.33
(B) 0.50
(C) 0.67
(D) 0.75
(E) 1.00
e. Which of the following is the most likely reason for the observed differences in the frequency of the G allele
between 1965 and 1972?
(A) Emigration of white moths from the population
(B) Chance
(C) Selection against gray phenotypes
(D) Speciation
(E) Mutation
7. The observed phenotypes for the MN blood group of an island population of 1,000 individuals are as follows:
MM MN NN
200 200 600
a. What are the phenotypic frequencies for this population?
b. What are the allele frequencies in this population?
c. What are the expected genotypic frequencies for this population?
d. Is the population in Hardy-Weinberg equilibrium?
8. A gene suspected of causing hypertension in humans was observed at the following genotype frequencies:
A1A1 0.575, A1A2 0.339, and A2A2 0.087. Analyze whether the gene is in H-W equilibrium (Note: the sample
size in this study was so large that a difference of 3% or more in any of the observed versus expected
frequencies indicated a statistically significant difference)