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Archiver > GENEALOGY-DNA > 2005-08 > 1123186491


From: "gareth.henson" <>
Subject: Re: [DNA] SNP mutation rates
Date: Thu, 4 Aug 2005 21:14:51 +0100
References: <IGEOKAGLHNEKPCKPADIGOEIKKEAA.bbailey.lowedna@baileyconnection.com> <REME20050803190044@alum.mit.edu> <090b01c59884$6238c5c0$0200a8c0@c452380a> <REME20050803194536@alum.mit.edu> <097001c59905$fff2b6f0$0200a8c0@c452380a>


Earl

it is true that if you sequenced a randomly selected set of junk Y
chromosome bases on a random set of human males, most of the results would
show no variation at all. But the YCC tree SNPs are not randomly chosen
locations, they are precisely those bases found so far that show consistent
and regularly detectable patterns of variation (a few private ones appear to
have sneaked in at the lowest levels). They are the needles in a very large
haystack. So it is not counter-intuitive that every man has at least some of
the SNPs in the tree, they are precisely the ones we need (or some of them)
to make this true as often as possible.

Only at the lowest levels do we find it harder to guarantee that everyone is
positive for an end node SNP, because the tree is wider, the time depth is
shallower and (in Europe at least) strong founder effects are rarer.

Gareth


----- Original Message -----
From: "Earl Beaty" <>
To: <>
Sent: Thursday, August 04, 2005 4:05 PM
Subject: Re: [DNA] SNP mutation rates

snip>
> The two of you are convincing that it is very
> unlikely that any living man has the full set of SNPs of Y-Adam. I hadn't
> considered that situation. But one of the reasons we don't see a very
large
> number of distinct haplogroups is because we have not tested all those
> options. For this discussion wouldn't it be better to restrict the range
of
> SNPs to those which have been actually found? The 2005 chart has something
> like 200-300 defined. With such a small number in consideration I would
> expect that many, perhaps most, men would have none of the observed
> mutations. This issue has obviously been well considered and understood. I
> just find it counter-intuitive.
>
snip
>
> --Earl


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