Native Americans descended from a single ancestral group, DNA stud...(ontained the 9-repeat allele short stret...)

Date:4/29/2009

ontained the 9-repeat allele, short stretches of DNA on either side of it were characterized by a distinct pattern of base pairs, a pattern they seldom observed in people without the allele. "If natural selection had promoted the spread of a neighboring advantageous allele, we would expect to see longer stretches of DNA than this with a similarly distinct pattern," Schroeder said. "And we would also have expected to see the pattern in a high frequency even among people who do not carry the 9-repeat allele. So we can now consider the positive selection possibility unlikely."

The results also ruled out the multiple mutations hypothesis. If that had been the case, there would have been myriad DNA patterns surrounding the allele rather than the identical characteristic signature the team discovered.

"There are a number of really strong papers based on mitochondrial DNA which is passed from mother to daughter and Y-chromosome DNA which is passed from father to son that have also supported a single ancestral population," Schroeder said. "But this is the first definitive evidence we have that comes from DNA that is carried by both sexes."

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Contact: Liese Greensfelder lgreensfelder@ucdavis.edu 530-752-6101 University of California - Davis Source:Eurekalert

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