Under what circumstance might measuring the frequency of homozygous recessive genotypes lead to erroneous predictions of allele frequencies in a population?

Question

Quizplus · Accepted Answer

Heterozygote advantage can maintain higher frequencies of heterozygotes than expected under Hardy-Weinberg equilibrium, leading to inaccurate predictions of allele frequencies if only homozygous recessive genotypes are measured.

Under What Circumstance Might Measuring the Frequency of Homozygous Recessive