Archiver > GENEALOGY-DNA > 2010-03 > 1268628836

From: "Ken Nordtvedt" <>
Subject: Re: [DNA] Clades, Definitions, Discoveries, FTDNA
Date: Sun, 14 Mar 2010 22:53:59 -0600
References: <>,<SNT115-W100A5F4E30C0231B9E890ACC2E0@phx.gbl>,<016301cac3e3$fe0b33e0$5e82af48@Ken1><SNT115-W196CFB24CCDD653D7C3D50CC2E0@phx.gbl>

----- Original Message -----
From: "Steven Bird" <>

> Let's do the numbers:
[[That's sure welcome; some one around here who wants to do the numbers ]]
> There were 134 million births last year, according to the U.N. estimates.
> Half of these were boys, so about 67 million boys. The odds of a SNP
> occurring, according to Hartwell 2008, are 1 in a billion. That means
> that there is just a 6.7% chance of a Y-SNP occurring within ONE birth
> among those 67 million boys last year. Following your logic, on average,
> ONE new SNP occurs among all births every 15 years or so. However, since
> the new SNP is always de novo and can occur anywhere, and there are 3
> billion base pairs in the human genome, the odds of any one SNP being
> duplicated are 3.0 * 10 to the -17 power.

[[ For purposes of the Y tree we are only interested in the mutations at
base pairs on the y chromosome. I'll take 25 million base pairs in the y as
the practical region.

67 males were born last year. EACH base pair on the y has your one in a
billion chance of mutating. So EACH base pair had a .067 chance of mutating
last year. So EACH base pair had a chance of approximately ONE to mutate
over about 16 years. That's half a generation --- so in half a generation
EACH and every practical snp site on the y chromosome has on average mutated
once. I still don't know why you are bringing the 3 billion base pairs of
the whole genome into the picture. The snps used for the male y tree are
only from the y chromosome. Ken ]]

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