Biology
Extra Credit
Name ________________________________
Population Genetics Problem Set-KEY
1. 6,120 people were tested for the MN blood group antigens (recall that M and N are
codominant). 1,778 had the blood type MM; 3,039 had the blood type MN, and 1,303 had
the blood type NN. What are the frequencies of the M and N alleles?
2. In fruit flies, brown body is dominant to black body. In a certain population of fruit flies, the
frequency of the brown body allele is 0.7.
a. What is the frequency of the black body allele?
b. If the population is in Hardy-Weinberg equilibrium, what percentage of the population
has the brown body phenotype?
3. In a different population of 400 fruit flies, the frequency of the black body allele is 0.25.
According to Hardy-Weinberg, how many flies should there be of each genotype?
4. In fruit flies, forked bristle is a recessive trait. In a population of flies, the frequency of
the forked bristle allele is 0.62. If the population is in Hardy-Weinberg equilibrium:
a. What is the frequency of normal bristle flies?
b. If the population consists of 2500 flies, how many of them are heterozygous?
5. You have sampled a population in which you know that the percentage of the
homozygous recessive genotype is 36%. Use this to calculate the following:
a. The frequency of the “aa” genotype.
b. The frequency of the “a” allele.
c. The frequency of the “A” allele.
d. The frequencies of the genotypes “AA” and “Aa”.
6. Within a population of butterflies, the color brown (B) is dominant over the color white
(b). 40% of all butterflies are white. Calculate the following:
a. The percentage of butterflies in the population that are heterozygous.
b. The frequency of the homozygous dominant individuals.
7. Ear lobes in humans can be either attached or unattached. The allele for free ear lobes
(F) is dominant over the allele for attached ear lobes (f). Suppose that in a population of
10,000 individuals, there are 8,400 people that have free ear lobes. Calculate the allele
frequency and also the proportion of people with each of the three genotypes.
8. A population of beetles contains 64 with brown wings and 36 with black wings. Black
wings are recessive. What proportion of the brown-winged beetles are homozygous
and what proportion are heterozygous?
9. What is the frequency of the heterozygotes (Aa) in a population in which the frequency
of all the dominant phenotypes is 0.25 and the population is in Hardy-Weinberg
equilibrium?
10. You are investigating coat color in mice, a co-dominant trait. Coat color is represented
by three phenotypes, black, gray, and white, where white is WW, black is BB, and
heterozygotes are gray. In a sample of 100 mice from this population, you find 60 with
black coats, 10 with gray coats, and 30 with white coats. Calculate the allele and
genotype frequencies in this sample.