Archiver > GENEALOGY-DNA > 2003-11 > 1069305768

Subject: Re: [DNA] Marker DYS390 in World database
Date: Thu, 20 Nov 2003 00:23:00 -0500 (EST)
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Brian wrote:
> Regarding mutation rates for STRs, has anyone observed in their surname
> projects whether it depends at all on the average number of years per
> transmission (or per generation)?

The effect is too small, and, especially, the mutation rate is too
small for any one project to detect the effect. Nonetheless, the
effect is probably there. It's just that replication slippage occurs
only during replication, which in turn occurs only when cells divide.
There must be dozens of cell divisions between conception and
maturity, but the rate of cell division slows down at maturity (one
exception being the inside of the mouth). Thus, the effect of age on
Y STR mutations must be much less than on, say, radiation-induced damage
(which can happen at any time).

Note, by the way, that somatic mutations (e.g., those that occur in
the cheek cells) are not passed on to descendants, and it is therefore
possible (though not likely) to detect a mutation in somebody without
finding it in that person's father or sons. The effective rate of
such somatic Y STR mutations would be much less than the germline rate
because the testing procedure averages together many cells, whereas
procreation takes just one cell and makes MANY copies.

John Chandler

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