Question

3. Suppose a population is carrying a condition controlled by two alleles: A (dominant) and a (recessive). Only homozygous individuals that have two copies of the recessive allele have the condition. If the a allele has a frequency of 20%, and the A allele had a frequency of 80%, what percentage of the population will have the condition? A. 80% B. 64% C. 4% D. 20%

Answer 1

C. 4%

To have two copies of the recessive a allele, consider acquiring the a allele twice as two independent events (multiply probabilities).

(.2)(.2) = .04 = 4%