GENEALOGY-DNA-L Archives
Archiver > GENEALOGY-DNA > 2002-08 > 1030374722
From:
Subject: Re: [DNA] How specific is 12 marker test
Date: Mon, 26 Aug 2002 11:12:02 EDT
In a message dated 08/26/02 7:52:47 AM Pacific Daylight Time,
writes:
> RE : "FamilyTreeDNA can't have more than about 5000 samples in their data
> base, that in this case he matched 24 of them. That was 1 in 200 (counting
> William himself). It could be even lower if they have included mtDNA
> samples are included in this database. So I question the 1 in 1000 number."
>
> I speculate that William has one of the more common sets and others have
> reported 4 and zero matches
> thus it does vary.
>
Yes, Bill McCeney has the Atlantic Modal Haplotype.
I've never seen distribution data on the whole 12 marker FTDNA set, but we
can take the Y STR database as a reasonable approximation. They have over
10,000 records, "randomly" selected from the local populations. They may not
be truly random, but there are presumably no clusters of families such as you
would find in the FTDNA database surname projects.
http://www.ystr.org/europe -- click on haplotype characteristics
The "haplotype diversity" for the 11-marker Y STR database is .9987. The
probability of finding a match if you pick two people at random is 1 - .9987,
or .0013, or as John suggested, about one in a thousand.
The single most common haplotype is found in 1.76% of the records.
Most haplotypes are rare. The "discrimination capacity" is 66%. I believe
that means that 66% of the haplotypes occur only one time in the database of
10,000. We've seen a number of cases on this list where the person has no
matches in the database, even without considering YCAII.
Now, before you take the 12-marker test, you don't know if you are going to
have a common or rare haplotype, but the odds are that it will be rare. After
you take the test, you can revise your own probability of finding matches
upward or downward from the 1 in a 1000 number.
Ann Turner
GENEALOGY-DNA List Administrator
http://lists.rootsweb.com/index/other/Miscellaneous/GENEALOGY-DNA.html
DNA preservation kits: http://www.dnafiler.com
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