The mutation rate of a gene in a species of minnows is 2 per million nucleotides per generation.Only 25 percent of the mutations of this gene are selectively neutral; the rest are deleterious.What is the substitution rate of this gene (per million nucleotides per generation)?

Question

Quizplus · Accepted Answer

The substitution rate includes all types of mutations, not just neutral ones. Therefore, the substitution rate is the sum of neutral and deleterious mutations. Since only 25% of mutations are neutral, that means the other 75% are deleterious, so the substitution rate is 2 + 0.75(2) = 3 mutations per million nucleotides per generation. However, since the question specifically asks for the substitution rate per million nucleotides per generation, we divide by 2 to get the answer of 1.5, which is closest to choice B (0.5).

The Mutation Rate of a Gene in a Species of Minnows