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Archiver > GENEALOGY-DNA > 2006-01 > 1136419787


From: (John Chandler)
Subject: Re: [DNA] Y-STR Mutation rate
Date: Wed, 4 Jan 2006 19:09:47 -0500 (EST)
References: <4.3.1.2.20060104144302.01fde180@mail.spacey.net><REME20060104163853@alum.mit.edu> <p06230907bfe1fab582c8@[192.168.1.104]>
In-Reply-To: <p06230907bfe1fab582c8@[192.168.1.104]> (message from Pat Oliveron Wed, 4 Jan 2006 16:41:57 -0600)


Pat wrote:
> John, I asked, however lamely, a year or so ago, when does a
> father-son mutation actually occur? You say it is fixed at birth. I
> agree but does it actually occur at conception when the sperm hits
> the egg or immediately thereafter?

No, it most likely occurs before or during sperm production. The
mechanism of STR slippage is not well enough understood to place
firm bounds on when it occurs, but the usual assumption is that it
occurs during cell division. There has been at least one study of
sperm cells that found STR mutations within an individual's sperm
at a rate comparable to the rate determined by looking at father-son
pairs, and so it is not necessary to assume mutations occurring
between conception and birth. On the other hand, I don't know of
any studies comparing buccal with blood test results to see whether
there are non-negligible numbers of differences.

John Chandler

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