GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2003-01 > 1043851134
Subject: Re: [DNA] A Eureka moment or not? Paternity test possibility
Date: Wed, 29 Jan 2003 09:38:54 EST
In a message dated 01/27/03 11:14:18 PM Pacific Standard Time,
> Now Mary has two X chromosomes--one from her
> father and the other from her mother. You dad has a 50% chance of
> having got his X chromosome from his grandfather (whether its a Totino
> male or another male).
I got bogged down trying to work through whether testing the X chromosome
would have any advantage over the traditional paternity (i.e. relationship)
tests. As Rik mentioned, Mary's two X chromosomes would swap material with
each other at the time she is creating a single X chromosome to go in the
egg. But that might actually be better for your situation: instead of being a
50-50 either-or situation, where your friend's Dad either gets his
grandfather's X chromosome or he does not, he would get (on the average) 50%
of his grandfather's X chromosome. He could get more or less, and his
siblings would also inherit random chunks of the grandfather's X chromosome.
One of the aunt's X chromosomes, on the other hand, would be a replica of the
grandfather's X chromosome.
There are a number of X chromosome STRs which have been described for
forensic purposes, but I don't know if you could get them tested
commerically. Here's one article I found in PubMed. This URL ends with the
Forensic Sci Int 2001 Dec 27;124(2-3):215-8
16 X-chromosome STR loci frequency data from a German population.
Edelman J, Hering S, Michael M, Lessig R, Deischel D, Meier-Sundhausen G,
L, Plate I, Szibor R.
Institut fur Rechtmedizin, Universitat Leipzig, Germany.
But don't rule out traditional paternity testing. Aunt/nephew share about 25%
of their markers, and first cousins about 12.5%. If the relationship is just
through one parent, then you would cut those numbers in half. The testing
laboratory would run some calculations on whether the relationship is more
likely to be full or half. The more people who are tested, the better the
chance of reconstructing the grandparent's markers, so it could get quite
expensive. And as Chris Scott has pointed out, you can sometimes get funny
distributions of markers.
If you search the archives for the phrase "relationship testing" you'll find
some other messages I've posted about selecting testing laboratories, etc.
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