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Archiver > Scotch-Irish > 2011-05 > 1304320995


From: "John Polk" <>
Subject: Re: [S-I] 25 marker DNA
Date: Mon, 2 May 2011 03:23:33 -0400
References: <676923083.4542503.1304300850206.JavaMail.root@sz0048a.emeryville.ca.mail.comcast.net>


Judy -

The simple answer is no. It is time to get an upgrade to 67 markers and see
what turns up there. A 25/25 match is only a first level check. It is good
for ruling out relationships but not for proving them. I have seen plenty of
cases where further testing, i.e. going from 25 to 67 makers, turns up
multiple mismatches in the remaining 42 markers, implying that the nearest
common male line ancestor must be many generations back. Unfortunately some
of the testing services provide misleading statements based on limited
marker results when they suggest that two persons had a most recent common
male line ancestor a certain number of generations back. The uninitiated
take this very literally and get very excited about finding close new
cousins but then get very frustrated when they can't find any connections
between their family lines. That happened to me when I got my first results.

DNA is very heplful but it is a only a supplement, not a replacement for,
good old paper trail research. There is no certain conclusion that you can
draw as to the exact closeness of a relationship without other evidence
beyond the DNA. It is always a matter of probabilities, not certainties. It
is quite possible for all the descendants of a single progenitor to inherit
his identical 25 or even 67 marker DNA for multiple generations before a
marker mutation occurs. Third, fourth and fifth cousins will usually have
perfect matches, or at most a single mismatch. Marker mutations are random
and infrequent and there is just no telling when one might occur. And keep
in mind that whenever a mutation does occur then you get a case where two
people only one generation apart, i.e. father and son, or two brothers, do
NOT have a perfect match.

DNA Testing is a very useful tool but understanding the results is tricky
and a lot more complicated than the testing companies lead you to believe
when you first sign up.

John Polk




----- Original Message -----
From: "Judy Anderson" <>
To: <>
Sent: Sunday, May 01, 2011 21:47
Subject: [S-I] 25 marker DNA


>
>
> Hello List,
>
>
>
> I was hoping if someone might tell me if a perfect 25 marker DNA test is
> good to rely on?
>
>
>
> Regards
>
> Judy Anderson
>
>
>
>
>
>
>
>
> -------------------------------
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