Cystic fibrosis, a recessive genetic disease, occurs in a particular population in approximately 1 of every 2,000 births. What is the frequency of carriers in this population?
You are given the frequency of affected individuals, 1 in 2,000, or 0.0005. This is the frequency of the genotype aa, which is equal to q2. Therefore, q is equal to 0.0224. Since we know q, we also know p (1 – q = 0.9776). In a population, carriers are heterozygotes, individuals who carry the allele but are not affected by it. The formula to calculate the frequency of heterozygotes is 2pq. therefore, the frequency of carriers in this population is 0.0438.