Evidence for higher rates of nucleotide substitution in rodents than in man.

TLDR

Rodent genomes evolve faster than human genomes, a pattern that aligns with neutral theory and is plausibly due to rodents’ shorter generation times and higher mutation rates. The study discusses how these faster substitution rates affect molecular phylogenetic analyses. Comparisons of coding regions, untranslated regions, and beta‑globin gene family members show that rodents accumulate roughly twice as many synonymous substitutions and 1.3 times as many nonsynonymous substitutions as humans, with even higher rates in UTRs (2.6–3.1×).

Abstract

When the coding regions of 11 genes from rodents (mouse or rat) and man are compared with those from another mammalian species (usually bovine), it is found that rodents evolve significantly faster than man. The ratio of the number of nucleotide substitutions in the rodent lineage to that in the human lineage since their divergence is 2.0 for synonymous substitutions and 1.3 for nonsynonymous substitutions. Rodents also evolve faster in the 5' and 3' untranslated regions of five different mRNAs; the ratios are 2.6 and 3.1, respectively. The numbers of nucleotide substitutions between members of the beta-globin gene family that were duplicated before the man-mouse split are also higher in mouse than in man. The difference is, again, greater for synonymous substitutions than for nonsynonymous substitutions. This tendency is more consistent with the neutralist view of molecular evolution than with the selectionist view. A simple explanation for the higher rates in rodents is that rodents have shorter generation times and, thus, higher mutation rates. The implication of our findings for the study of molecular phylogeny is discussed.