Archiver > GENEALOGY-DNA > 2010-02 > 1266192560

From: (John Chandler)
Subject: Re: [DNA] TMRCA assessments
Date: Sun, 14 Feb 2010 19:09:20 -0500
References: <><A597BD8569E24290A10B37465204E6B5@anatoldesktop><525460709C6A493EBD3D6BECD514B319@john>
In-Reply-To: <525460709C6A493EBD3D6BECD514B319@john> (

John wrote:
> I have not checked what the current estimates of mutation rates are on the
> faster markers, and they may have changed a bit from when I originally
> extracted data. However, some time ago, the following was quoted as the
> mutation rates for the following markers...
> DYS576= 0.015 (1 mutation every 66 transmissions)
> DYS570= 0.014 (1 mutation every 71 transmissions)
> CDYa= 0.017 (1 mutation every 59 transmissions)
> CDYb= 0.017 (1 mutation every 59 transmissions).

These CDY rates agree with mine, but the other two are rather higher
than mine. Nonetheless...

> That means that for the group of 9 haplotypes, there are 9x11=99
> opportunities for each marker to mutate.

For a 37-marker analysis, using my mutation rates, the probability is
about 96% of getting at least one case of two or more mutations on the
same marker during 99 opportunities. However...

You do NOT know that there will be 99 mutation opportunities in a tree
with nine descendants after 11 generations. This is one aspect of the
point that Ken has been making so forcefully. It's unlikely that the
MRCA had nine sons all represented in the sample of testees, and so
the number of mutation opportunities will be reduced from the
theoretical maximum by some amount. This reduction is a problem,
unless you have paper evidence to pin down the exact structure of the

John Chandler

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