WEAK MALE-DRIVEN MOLECULAR EVOLUTION IN RODENTS

In humans and rodents the male-to-female ratio of mutation rate (alpha(m)) has been suggested to be extremely large, so that the process of nucleotide substitution is almost completely male driven. However, our sequence data from the last intron of the X chromosome-linked (Zfx) and Y chromosome linked (Zfy) zinc finger protein genes suggest that alpha(m) is only approximate to 2 in rodents with a 95% confidence interval from 1 to 3. Moreover, from published data on oogenesis and spermatogenesis we estimate the male-to-female ratio of the number of germ cell divisions per generation to be approximate to 2 in rodents, confirming our estimate of alpha(m) and suggesting that errors in DNA replication are the primary source of mutation. As the estimated alpha(m) for rodents is only one-third of our previous estimate of approximate to 6 for higher primates, there appear to be generation-time effects-i.e., alpha(m) decreases with decreasing generation time.