Varying Patterns of Mutation: Measuring the Universality of Regional Mutation Rates

Abstract

Mutations are the ultimate source of genetic variation in DNA. The patterns of mutation, however, can vary both within and across genomes. It has previously been shown that several mammals have heterogeneous mutation rates, while four yeasts have been observed to have uniform rates. The generality of these observations has not been known. Here we examine silen tsite substitutions in coding regions of 20 mammals, 27 yeast, and 4 insects, to determine which genomes demonstrate this mosaic rate distribution and which are uniform. Our findings show that mutational heterogeneity occurs in all branches of the mammalian phylogeny, as well as in flies and mosquitoes. All yeasts have a uniform rate across their genomes with the exception of three candida species: c. albicans, c. dubliniensis, and c. tropicalis. We hypothesize that this is due to the lack of sexual recombination in these species, leading to the regional accumulation of mutations.