Question

Imagine we have two diploid species which diverged 10 million years ago. On sequencing part of an autosome where we think most of the mutations are neutral we find that they are 20% divergent.

if we estimate that both species go through 4 generations per year, what is the mutation rate per site per generation?

Answer 1

Let's say the genome is only 100 base pairs long.

In that case, 20% of the genome, or 20 base pairs mutated in within a span of a million years or 10⁶ x 4 = 4 million generations.

Hence, mutation rate per site per generation = 20 / 4,000,000 = 5 x 10^-6

Since the genome size of the organism is not given, we can proceed no further. If the genome size is N bp, mutation rate per site per generation

20% of N 4 million 20. N 100. 4,000,000 = 5N x 10-8