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Archiver > GENEALOGY-DNA > 2006-11 > 1162593475


From: "Ken Nordtvedt" <>
Subject: Re: [DNA] Molecular clocks: when times are a-changin'
Date: Fri, 3 Nov 2006 15:37:55 -0700
References: <000201c6ff94$7cbe8060$4001a8c0@BigMem2>


----- Original Message -----
From: "John McEwan" <

I have also detailed a
> number of times how genetic variation in an individuals capacity to
> repair mutations produces correlated changes in both STR and SNP
> mutation rates across the genome. Therefore "observed" father son rates
> will be by definition be an overestimate of the observed change over a
> longer time frame because the effect of purifying selection has not been
> explicitly accounted for. Currently the magnitude of this effect is
> difficult to estimate, but it should not be ignored.



Rather than just toss out a buzz word term like "purifying selection", would
you please explain why the 15 at DYS388 in my ancestral line might be
purified or selectively driven back to the founding 14 through the hundreds
of generations since the I1a founder? Why would "15" repeats at DYS388 have
a tendency to be "repaired" and to what value? The founder of I1a had a 14
at DYS388 not because of some advantage or preference for that repeat
number --- it was the result of mutational chance in his previous line ---
and then for totally independent reasons he happens to be in the right place
at the right time to be a prolific founder of what we today call a
haplogroup.

You can't drag in "selection" as a factor without spelling out what might be
selected for in the length of these STRs?

More explanations please! Ken


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