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 <em>candida</em> species: <em>c. albicans</em>, <em>c. dubliniensis</em>, and <em>c. tropicalis</em>. We hypothesize that this is due to the lack of sexual recombination in these species, leading to the regional accumulation of mutations.
Highlights
Popular understanding of gene mutations often focuses on those that have obvious effects, such as insects that develop resistance to pesticides
Uniform mutation rates have been observed only i n the phylogeny of the sensu stricto yeasts S. cerevisiae, S. paradoxus, S. bayanus, and S. mikatae.vm I n these species, neutral mutations occur at the same rate i n the entire genome
Species pairs from two subclades [(C. albicans, C. dubliniensis, C. tropicalis) and (N. crassa, C. globosum)] were found to have distributions that did not fit the normal curve
Summary
Popular understanding of gene mutations often focuses on those that have obvious effects, such as insects that develop resistance to pesticides. Uniform mutation rates have been observed only i n the phylogeny of the sensu stricto yeasts S. cerevisiae, S. paradoxus, S. bayanus, and S. mikatae.vm I n these species, neutral mutations occur at the same rate i n the entire genome. The reason for this differing mutational behavior is not known, and little is known about regional biases i n other species. Most previous studies of mutation rate variation have focused on mammals, including human, chimp, mouse, rat, dog, and cow. We answer the questions: Do all mammals exhibit heterogeneity i n their mutation rates? Do all yeasts exhibit uniformity? Studying these phylogenies together provides a valuable contrast
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