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Archiver > GENEALOGY-DNA > 2002-03 > 1017103135


From: "Allan S. Gleason" <>
Subject: Re: [DNA] Confidence in labs
Date: Mon, 25 Mar 2002 17:38:55 -0700
References: <10889-3C9F4DEB-1071@storefull-2138.public.lawson.webtv.net> <5.1.0.14.2.20020325142709.00b90a70@pop.erols.com>


"George W. Page" wrote:
The results of their Y-Line test consisted of ten markers:

> DYS 19; DYS 388; DYS 390; DYS 391; DYS 392; DYS 393; DYS 389i; DYS 389ii-i
> ; DYS 425; and DYS 426.
> (See how nice it is to display them in numerical order!)

Much better! But of course, 389i and 389ii-i should follow 388

> How many markers does it take to properly identify/fingerprint somebody?

Considering that six of those markers are used to identify you as European - and not
very well at that, I feel comfortable with FTDNA's 21 markers or Relative Genetics'
23 markers - especially when we know more about them and how they behave. FTDNA
has shown from their relatively small database far too many "hits" between people
who have no genealogical connection at all using their minimal twelve marker test.
There is, of course, a practical limit on how many markers can be used but I think
that 10 or 12 are inadequate.

The problem is that if you look at the individual marker frequencies there is
usually one primary state and perhaps two or three other less frequent repeat
counts. Lets be generous and say that with 12 markers with 4 coequal states there
would be about 500 combinations. By sampling populations in the millions it would
seem to me that there could be many duplications. Using 22 markers the number of
combinations would be over 7,000. Even then there wouldn't be any guarantees of
uniqueness, but the numbers are significantly better. Now I know that the math is
not that simple, but I think the principle is true. The thing that makes each of us
unique is the fact that we have thousands of markers - the kind that actually mean
something.

George, are you a member of a Page surname group? Since my 8th great grandmother
and matriarch of the American Gleason family was a Page and we have no documented
idea of her parentage I'd be interested in knowing about your group. The one thing
I do know is that you don't do a google search for Page! Been there done that! :>)

Allan



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