You are working for the Peace Corps in New Guinea and notice that about 4% of individuals have a debilitating disease. After doing a pedigree analysis, you determine it is an autosomal trait that shows a recessive expression pattern. What is the frequency of the deleterious (harmful) allele in the population?

0.2 or 20%

Explanation:

Assuming that the population is in Hardy-Weinberg equilibrium:

p + q = 1

p² + 2pq + q² = 1 where,

p = frequency of dominant allele

q = frequency of recessive allele

p² = frequency of homozygous dominant genotype

2pq = frequency of heterozygous genotype

q² = frequency of homozygous recessive genotype

Here,

since the trait is autosomal recessive, q² = 4% or 0.04

Frequency of recessive harmful allele = q

= √0.04

= 0.2 or 20%