GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2007-03 > 1173913380


From: (John Chandler)
Subject: Re: [DNA] OmniPop caution received from FamilyTreeDNA
Date: Wed, 14 Mar 2007 19:03:00 -0400 (EDT)
References: <cdb.9c8bb2a.33283343@aol.com> <45F6F8C5.9030209@sbcglobal.net> <45F767C0.9010501@mchsi.com> <45F78B4D.7020001@sbcglobal.net> <40A3F6B4-5ED4-4C59-BF0B-E33FC2572CEC@vizachero.com> <45F85441.90702@sbcglobal.net><F389E53E-15B0-4A02-8308-9CCF1D9E35F1@vizachero.com><45F86F1C.6060509@sbcglobal.net>
In-Reply-To: <45F86F1C.6060509@sbcglobal.net> (aburto@sbcglobal.net)


Al wrote:
> Where is the fault with the method?

We discussed this a bit last time. The numbers that come out of any
of these population comparisons are simply probabilities (or
reciprocals of probabilities) that a member of the population in
question would have the stated genotype. There is nothing about
cross-bred individuals, mostly because such individuals do not
generally exist in enough numbers to constitute a recognized
population of their own. The important point here is that "high"
numbers for two separate populations cannot be interpreted as an
indication of admixture of those populations in the test subject, and
there are no numbers for comparison for the hypothetical mixed
populations, and so you can't say *anything* about someone of mixed
ancestry with this method (unless he or she happens to belong to a
mixed population that *is* included in the database).

Note: hypothetical mixed populations can easily be simulated, but
the correction factor for population size is all the more important
for such "fakes" and is uniformly "roughly zero" for all such.

John Chandler

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