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Archiver > GENEALOGY-DNA > 2002-08 > 1028307793


From: "Jim Huffaker" <>
Subject: Re: [DNA] Test Variability
Date: Fri, 2 Aug 2002 13:03:13 -0400
References: <158.11d3ff40.2a7b4c56@aol.com>


Thanks Ann for the instructive calculations. Please more: Ken and I match
counts at 21 of 23 loci except:
Counts Me Ken
DYS 390 23 24
DYS 392 11 13

From these RG estimated our common ancestor lived around 1690. Which factors
are instrumental? The two loci that count different or the two count
difference in the one locus or are both equally important? What would
conclusions have been if Ken's DYS 392 count had been 12 or for that matter
if his counts for both loci were identical to mine. Is there reading or
examples on these calculations?



----- Original Message -----
From: <>
To: <>
Sent: Thursday, August 01, 2002 10:45 PM
Subject: Re: [DNA] Test Variability


> In a message dated 08/01/02 1:23:31 PM Pacific Daylight Time,
> writes:
>
>
> > My brother and I were one count different at Y-GATA-A10. Thirteen for
me, 14
> > for him. All the other loci counts were identical. The testing company
just
> > remarked that it was unusual for brothers to not have identical counts
at
> > all loci.
>
> One of you has a mutation at that locus compared to your father. Mutations
> are random events and can occur at any time. You can figure out the
> probability of two brothers matching if you know the average mutation
rate.
> We generally use .002 per locus as the rate, although Relative Genetics
> appears to be using a higher number.
>
> If you are looking at one locus, the "expectation" of matching your father
is
> .998. If you are looking at two loci, the expectation is .998 x .998,
three
> loci is .998 x .998 x .998, etc. The expectation of matching at all 24
loci
> is .998 ^ 24, or .953. The expectation that you will match your brother is
> .953 x .953 = .908. So the probability of a mismatch is .092, which
probably
> qualifies as "unusual" but not "astonishing." RG probably doesn't test
many
> brothers -- it's more common to look for distant cousins to confirm their
> common ancestor.
>
> A number of people have had tests performed by different laboratories, and
I
> don't recall any recent cases of discrepant results. (There were some
> calibration questions early on.) Of course any laboratory procedure is
> subject to error, including "clerical mutations" where results are simply
> copied to the wrong column. But I'd feel comfortable saying that you and
your
> brother now have distinctive haplotypes -- which may prove useful to your
> future descendants!
>
> Ann Turner
> GENEALOGY-DNA List Administrator
> http://lists.rootsweb.com/index/other/Miscellaneous/GENEALOGY-DNA.html
> DNA preservation kits: http://www.dnafiler.com
>
>
> ==============================
> To join Ancestry.com and access our 1.2 billion online genealogy records,
go to:
> http://www.ancestry.com/rd/redir.asp?targetid=571&sourceid=1237
>
>
>


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