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From: "Anatole Klyosov" <>
Subject: Re: [DNA] TMRCA assessments
Date: Sat, 20 Feb 2010 19:18:54 -0500
References: <mailman.435.1266307243.25640.genealogy-dna@rootsweb.com>


> From: "Alister John Marsh" <>
> Anatole,
> If a marker mutates once, and has a second mutation after a period of
> time,
> the second mutation has roughly 50% chance of being a back or forward
> mutation. Perhaps that was what David was meaning. Is that not correct?

My response:

This is correct. However, for datasets descending from the same ancestor who
lived less than 26 generations ago there are VERY few "second mutations" at
the same locus. Overall, their contribution is VERY minimal. 50% of it will
be even less.

Instead of talking in general, I suggest you to take such as a dataset as an
example, and count what is a percentage of those "second mutations" among
all mutations.

The problem is people here often talk generalities instead of considering a
concrete example to illustrate their point.

I have asked many times here what is a contribution of "parallel mutations"
in a dataset, say, L21, or M222, or whatever. Those datasets are easily
available, Nobody goes for it. This is a mystery to me. I was trained -
when I talk about numbers, I take numbers, and show the case. Is that so
difficult?

Regards,

Anatole


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