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The pattern of nucleotide difference at individual codons among mouse, rat, and human
Robert Friedman1, Austin L Hughes
1Department of Biological Sciences, University of South Carolina, USA.
Molecular Biology and Evolution
|February 18, 2005
Summary
Researchers compared nucleotide differences in genes shared by humans, mice, and rats. Rats showed more genetic differences from humans than mice did, but multiple gene changes in rodents were as expected by chance.
Area of Science:
- Comparative genomics
- Mammalian evolution
Background:
- Understanding genetic divergence between species is crucial for evolutionary studies.
- Previous research suggested differing rates of genetic change between rodents and humans.
Purpose of the Study:
- To compare nucleotide differences across orthologous genes in humans, mice, and rats.
- To investigate the frequency of synonymous and nonsynonymous substitutions.
- To re-evaluate the occurrence of multiple nonsynonymous substitutions in rodents.
Main Methods:
- Analysis of 3,473,111 codons from 9,390 aligned orthologous genes.
- Comparative nucleotide sequence analysis across Homo sapiens, Mus musculus, and Rattus norvegicus.
Main Results:
- A higher frequency of both synonymous and nonsynonymous nucleotide differences was observed between rats and humans compared to mice and humans.
- No evidence supported a higher-than-expected frequency of codons with multiple nonsynonymous substitutions between rats and mice.
Conclusions:
- Rats exhibit a greater degree of genetic divergence from humans than mice do.
- The pattern of multiple nucleotide substitutions between rat and mouse aligns with random processes.