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Archiver > GENEALOGY-DNA > 2010-03 > 1268661923


From: Vincent Vizachero <>
Subject: Re: [DNA] Clades, Definitions, Discoveries, FTDNA
Date: Mon, 15 Mar 2010 10:05:23 -0400
References: <270548.86246.qm@web111316.mail.gq1.yahoo.com>, ,<SNT115-W100A5F4E30C0231B9E890ACC2E0@phx.gbl>, ,<016301cac3e3$fe0b33e0$5e82af48@Ken1>,<SNT115-W196CFB24CCDD653D7C3D50CC2E0@phx.gbl>,<01ba01cac3fb$87b368d0$5e82af48@Ken1><SNT115-W3785126A2D053855EFBF3ACC2E0@phx.gbl>
In-Reply-To: <SNT115-W3785126A2D053855EFBF3ACC2E0@phx.gbl>


Steve,

Mutation rates are expressed in mutations per bp, not mutations per SNP.

There are 25 million (useful) bp on the Y chromosome, not 50,000. If
you want to know how many SNPs per birth you are likely to observe,
mutliply the mutation rate (which is closer to 1-in-30 million bps,
actually, for the Y) by the number of observed sites.

(1/30,000,000) * 25,000,000 = .83

That is, we should observe a Y-SNP difference every birth or two.

With billions of men on the planet, and only 25 million possible Y-SNP
locations, it must follow that every SNP is happening multiple times
per generation.

However, this is not cause for concern because - as Diana pointed out
- phylogeneticists always use the SNPs in the context of other SNPs.
If someone in J2 turns up L21+, that won't confuse us because it will
be obvious from all his other SNPs (M429,M304,M172, etc.) that he is
actually J2.

VV


On Mar 15, 2010, at 9:06 AM, Steven Bird wrote:

> If we have an average of about 50000 SNPs on the Y chromosome
> (that's 51 million BP divided by an average of 1 SNP every 1000 bp -
> I've rounded a bit for convenience) then the odds of any one SNP
> changing on any one site is .00005 per transmission, given a
> mutation rate of 1 mutation in 1 billion transmissions


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