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Mammalian genomes are mutating at similar rates, study finds
Edward R. Winstead


A new study reports that genetic mutations occur at similar rates for all genes in mammalian genomes. Furthermore, the genomes of different mammals have similar overall mutation rates. Mutations, such as the single 'letter' changes in DNA that occur naturally during evolution, are a source of essential diversity for a species as well as a cause of disease.

Detail of diagram showing mutational differences among mammalian species. View larger

To determine the extent of differences in mutation rates among mammalian genes and across genomes, Sudhir Kumar and Sankar Subramanian, both of Arizona State University in Tempe, conducted a computational analysis of nearly 5,700 genes. The gene sequences came from scientific databases and represent 326 species, including humans, mice, cattle, pigs, and dogs.

"We find that the mutation rate is approximately constant per year and largely similar among genes," the researchers write in Proceedings of the National Academy of Sciences. The new findings "argue against the widely held notion about large differences in mutation rates among genes in a genome and among major mammalian lineages."

Many of the previous studies reporting large differences in mutation rates involved limited numbers of genes or only a few species. Kumar and Subramanian point out that large numbers of genes and a diverse sample of species are prerequisites for computation analyses that aim to accurately track rates of evolutionary change.

"Our results suggest that the average mammalian genome mutation rate is 2.2 x 10-9 per base pair per year, which provides further opportunities for estimating species and population divergence times by using molecular clocks," the researchers write.

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Kumar, S. & Subramanian, S. Mutation rates in mammalian genomes. Proc Natl Acad Sci USA 99, 803-808 (January 22, 2002). Published online January 15, 2002.

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