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Archiver > GENEALOGY-DNA > 2003-11 > 1067734100


From:
Subject: Re: [DNA] Marker Mutation Rates
Date: Sat, 1 Nov 2003 19:48:20 -0500 (EST)
References: <5.0.2.1.2.20031101090758.02583ba0@mindspring.com>
In-Reply-To: <5.0.2.1.2.20031101090758.02583ba0@mindspring.com> (message fromRon Lindsay on Sat, 01 Nov 2003 11:32:55 -0800)


Ron wrote:
> continue to look for legitimate reasons to challenge the current thinking
> regarding the assumed Y-chromosome marker mutation rates.
>
> I would like to pose a question to the geneticists and mathematicians
> subscribing to this forum.
>
> Is it possible that a fallacy was introduced initially into the thinking
> regarding Y-chromosome marker mutation rates based in part on the fact that
> marker mutations can move back and forth (+1 or -1) over time and was not
> properly taken into consideration by geneticists also using "limited"
> database sizes??

Here is the short answer: NO.

> Unless someone can tell us that all this probability was indeed factored
> into the current "mutation rate equation",

Here is where you're going astray. You are presuming that extra mutations
will preferentially cancel each other out. There is no evidence that the
mutation process is non-random. Therefore, if the mutation rate is
higher than the nominal by some factor, then the extra mutations will
mostly show up as differences discernible in the measured haplotypes.

Indeed, the potential for cancellation is exactly why it is necessary
to add up the squares of the marker-by-marker differences when computing
the genetic distance between two people. (That is both necessary and
sufficient to account for possible cancellation.)

John Chandler


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