Two species of plants that diverged 20 million years ago have accumulated an estimated 10 nucleotide differences in gene X.Species A has had an average population size of 3 million, while species B has had an average population size of 0.5 million.Both of these plants are annuals, with one generation per year.Assuming that the substitutions are all neutral, what is the estimated neutral mutation rate of gene X per million generations?

Question

Quizplus · Accepted Answer

The neutral mutation rate is estimated as the number of nucleotide differences divided by the number of generations. In this case, the number of nucleotide differences is 10 and the number of generations is 20 million years * 1 generation per year = 20 million generations. Therefore, the neutral mutation rate is 10 / 20 million = 0.5 * 10^-6 per generation. Since the question asks for the rate per million generations, we multiply by 1 million to get 0.5 * 10^-6 * 1 million = 0.5 * 10^-3 = 0.25 * 10^-3 = 0.25 * 10^-3 per million generations.

Two Species of Plants That Diverged 20 Million Years Ago