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Archiver > GENEALOGY-DNA > 2003-11 > 1067908198


From:
Subject: Re: [DNA] Marker Mutation Rates [and MRCA]
Date: Mon, 3 Nov 2003 20:10:07 -0500 (EST)
References: <20031103055924.3287.qmail@web41211.mail.yahoo.com>
In-Reply-To: <20031103055924.3287.qmail@web41211.mail.yahoo.com> (message fromDavid Faux on Sun, 2 Nov 2003 21:59:24 -0800 (PST))


David wrote:
> Perhaps someone can illuminate why I should be jazzed to learn that
> the pattern of scores as reflected in a series of 3 mutations means
> that the Most Recent Common Ancestor (MRCA) of DKF and IAF is
> somewhere within the interval between present and 50 generations ago
> (at the 95% confidence interval). Gee, thats a whole lot of help.

Actually, it IS a whole lot of help. Consider the alternative -- for
two random people off the street, the chances are that the 95% confidence
interval would not include the present at all. You have been spared
that contingency.

> I am also beginning to wonder whether some Y chromosomes (i.e.,
> families) are likely to experience more mutations than others

That has always been a possibility, but so what? Some families
live in houses with high radon concentrations, or eat foods with
mutagenic pesticide residues. or experience various other factors
that might or might not influence the rate of replication slippage.
None of the evidence I've seen to date suggests, or even supports,
the notion of systematic biases in the mutation rates. The
statistics are not strong enough yet. Some day, but not now.

> Irrespective, the fact is that a mutation could
> supposedly occur at any marker in any generation.

Absolutely.

> What we
> need is a subset of markers known (from empirical evidence) to never
> mutate

That's no help at all. If it NEVER mutates, then, ipso facto, there
is no variation in the human population. What you're suggesting bears
a strong resemblance to UEPs, which are rare enough to be presumed to
have occurred only once in all time. Those are fine for population
studies, but virtually useless for genealogy.

> Based on the Kayser evidence FTDNA should include DYS390 among their
> "fast moving" markers,

No. The Kayser evidence is not statistically significant for any
individual marker. It was only by averaging them all together that
they got any kind of meaningful result.

> As it stands, neither mutation rates, nor the concept of the MRCA
> have any purpose whatsoever in my research.

Not explicitly, but you must understand that the entire context of
DNA studies is set by the average mutation rate. That context
determines the range of time spans that you can think about and
governs what you can get away with calling a "near-match". If
the rates were ten times higher than they are, you couldn't do
the same kind of research at all.

John Chandler


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