A University of Nebraska-Lincoln (UNL) researcher has contributed to discoveries about bird evolution as part of a new study that sequenced the complete genomes of 45 avian species. Published as the cover story of the December 12, 2014 issue of Science, the study found that avian genomes -- the complete archive of genetic material present in cells -- have exhibited surprisingly slow rates of evolution when compared with their mammalian counterparts. Dr. Jay Storz, a Susan J. Rosowski Associate Professor of Biological Sciences, led a research group that assisted the study by examining the evolution of multi-gene families shared by birds and mammals. Each family comprises a collection of genes related to one another through a history of duplication, with all members of a given family descending from a single ancient gene. Dr. Storz and his colleagues used computational methods to measure "gene turnover," the rate at which genes are gained or lost over time. The researchers reported that the rate of turnover in avian gene families is roughly two times slower than in mammals. This finding reflects a larger-scale pattern of evolutionary stasis in avian genomes, according to Dr. Storz. "In mammals, there's this continual turnover -- it's like a genomic turnstile. With birds, it's far more conservative," Dr. Storz said. "There might be a gene family that consists of, say, 10 members in the common ancestor of birds and mammals. In mammals, that gene family has probably expanded and contracted in different lineages, and this results in dramatic differences in gene family size and membership composition among contemporary species. In birds, those 10 ancestral gene copies will remain intact and are inherited by all descendant lineages, so very little variation accumulates among species."
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