Answer:
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%