Fraction of SNPs Can Affect Fitness

A point mutation analysis of the entire human genome finds that alterations to as many as 7.5 percent of nucleotides may have contributed to humans’ evolutionary split from chimpanzees.

By Kerry Grens | January 21, 2015

WIKIMEDIA, STEPHENCDICKSONResearchers have developed a new computational approach to understanding which single nucleotide polymorphisms (SNPs) in the human genome might have conferred species-specific advantages. Researchers from Cornell University in Ithaca, New York, and colleagues found that many such point mutations related to human evolution actually reside in noncoding regions of the genome.

According to the study, published in Nature Genetics this week (January 19), roughly half of the genetic alterations under selection were intergenic; another third were in introns. “These findings suggest that human evolution works mostly through changes in how genes are used, rather than by altering genes and the proteins they encode,” reported Science News.

According to the authors, their finding that less than 10 percent of nucleotide substitutions affect fitness “stands in contrast to estimates that ~80% of nucleotides may be functional, based on measures of ‘biochemical activity.’” The Cornell team added that such discrepancies could reflect different definitions of function. For instance, other estimates “do not account for sequences (such as spacer elements) that would have fitness consequences if deleted but not mutated,” the authors wrote in their paper.

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Avatar of: Hugh-F-61


Posts: 75

January 24, 2015

All DNA gets transcribed occasionally, if only as a trigger for the RNA-guided DNA methylase complexes to epigenetically shut it down again. That transcription isn't a "function", it is a symptom of junk DNA sequences.

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