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Archiver > DNA-R1B1C7 > 2009-04 > 1240794029


From: David Ewing <>
Subject: Re: [R-M222] Walk on the Y Project
Date: Sun, 26 Apr 2009 19:00:29 -0600


Ken Nordtvedt tells us that total branch length in generations divided by
500 gives the odds of finding a new SNP.

Knowing Ken, I do not doubt this. Still, I would like to know how he arrived
at that formula. I understand that single nucleotides mutate five orders of
magnitude more slowly than STRs. The mutation rate of single nucleotides is
something like 0.00000002, or one per nucleotide per 50 million generations.
But since there are about 60 million nucleotides in the Y-chromosome, we
should expect a little over one new SNP per generation, on average. I have
na idea that Ken's much smaller number results from the fact that not all 60
million nucleotides are being considered, and the Walk on the Y project is
looking at only one five-hundreth of these, but I certainly do not know.

Can someone help me understand this?

David Ewing

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