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Archiver > GENEALOGY-DNA > 2004-03 > 1080764728


From: "Terry Barton" <>
Subject: RE: [DNA] Some thoughts about the near future
Date: Wed, 31 Mar 2004 15:25:28 -0500
In-Reply-To: <20040331192417.89747.qmail@web20005.mail.yahoo.com>


Peter, I would think that the character of the specific additional markers
will also be quite important as the number of markers in a test increases.

We see FTDNA designating some markers as "fast moving". In fact, the
deductions that Doug McDonald did on the Sorenson site showed a range of
mutation rates of .0005 to .0075 - which is a factor of 15 of highest over
lowest. As the quantity of markers increases, it is likely that their net
average will be different from what we now see. The impact will much
different if the additional markers mutation rate averages at the "fastest"
rate of .0075 rather than the slowest rate of .0005. Doug came up with
overall "averages" of .0028 to .0031, depending on how he configured his
selection. (Doug's message was sent Sat 2/28/2004 10:30 PM according to my
saved copy)

There is also discussion about significant variations in mutation rates
among families which logically will become even more important as the number
of markers increases. (Our group of 57 men with the Barton Lineage I
Haplotype - we're probably R1b - has only 15 identifiable mutations in the
57 men, for a rate that is roughly half of "average")

I can imagine that we'll not be able to be as simplistic in our analysis at
50 - 75 - 100 markers as we are now. In fact, it sounds like the folks
analysing 37 markers are concerned about whether the mutations are on "fast
moving" markers in addition to the number of mismatches.

It seems possible that we will use the more stable portion of the markers to
determine relationship into a Haplotype or Lineage (like we do now) and then
use the fast movers to fine-tune relationships within a Haplotype or
Lineage.

Terry

-----Original Message-----
From: Peter J. Roberts [mailto:]
Sent: Wednesday, March 31, 2004 2:24 PM
To:
Subject: [DNA] Some thoughts about the near future


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



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