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Archiver > GENEALOGY-DNA > 2004-03 > 1080761057


From: "Peter J. Roberts" <>
Subject: [DNA] Some thoughts about the near future
Date: Wed, 31 Mar 2004 11:24:17 -0800 (PST)


Is it possible to estimate the percentage of close
matches that are expected to be due to convergence and
the percentage of close matches that are expected to
be due to relatedness (ancestry by descent)? How can
we be so sure that the various clusters of near
matches are not mostly due to Ghengis Khan type
situations or the prolificness of the those lines?

It would appear to me that a close match with a 100
STR marker test would make convergence less of a
problem than with a 12 or 25 marker test.

I would define close as 22/25 or better. I don't know
what close would be on a 37, 43, or "100" marker test.

Regarding my statment that it is predicted that at
about 140 STR markers, a y-chromosome test becomes a
personal identity test, what I was told was "Using
statistical models, the TMRCA approaches 1 as the
number of markers reaches about 140 and could
therefore work as an identity test at that level."

Thank you for this conversation. I don't always
understand but I continue to learn.

Thanks and sincerely, Peter

>>>>>>>>>>
From:
Subject: Re: [DNA] Some thoughts about the near future
Date: Mon, 29 Mar 2004 16:22:19 -0500 (EST)
References:
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In-Reply-To:
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Peter wrote:
>> I'm still curious if it is likely in the near
future
>> that convergence will not be a real factor in our
>> results.

John wrote:
>Convergence will always be a real factor in our
results. The point
>is that convergence operates at all time scales, and
so the most
>worrisome cases of convergence are those where there
have been only
>two mutations that happen to cancel each other out.
Neglecting the
>variability and asymmetry of mutation rates, you can
easily show
>that 2% of all cases with 2 mutations on 25 markers
do indeed cancel
>and show an exact match. No amount of SNP testing
will sort that
>out. The longer the time scale, the more likely that
SNP testing
>could help, but the less likely the scenario is
overall.

>John Chandler



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