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Archiver > GENEALOGY-DNA > 2008-09 > 1220715364


From:
Subject: Re: [DNA] 9RA Autosomal Native American Marker
Date: Sat, 6 Sep 2008 11:36:04 EDT


In a message dated 9/6/2008 12:24:08 AM Pacific Daylight Time,
writes:

> I did an analysis of the 19 repeat allele. In the Old World it is found in
> Arab Africa, a cluster of Arab tribes in Afghanistan and surrounds, then in
> a straight line to a Tibetan people residing in China to Inner Mongolia of
> China to the Yakuts and Mongolians to the north and there it stops. Now in
> the New World it is found in the Aleutians, across the Canadian Northwest
> Territories to the Dogrib and as far as one can go to east with the Innuit
> of Greenland. The direction is then central to the Sioux and southwest to
> the Chihuahua area of Mexico and finally south to the Maya of the Yucatan
> Penninsula and there it stops. There appears to be structure since there is
> nothing in Central Asia or Europe or the Pacific Islands but there is a
> linear path to or from Africa. If this represents a single founder effect
> the question becomes "where was the point of origin"? Was it Africa to the
> Arab world to nearby Tibet and Mongolia before crossing the Bering Straight,
> or did it start in the Tibetan area and bifurcate eastward and westward.
> Either way it must be a very old mutation. I can literally connect the dots
> on the map in the article and it shows a definite path to the New World with
> no detours. All of this may be just one big coincidence, but the fact is
> that there are ancestral informative markers and with D9S919 (D9S1120) it is
> possible that not only the shortest repeat allele, but also the longest
> repeat allele could be sending a signal that is there to be read. It at
> least deserves further study.

I suspect that some of those 19-repeat alleles are identical by state (IBS),
not identical by descent (IBD). The customary microsatellite mutation rates
would be applicable, so that 18 could easily mutate to 19 independently in
different parts of the world. The 9-repeat allele seems to be a special case, with
a very low mutation rate due to its short length. The number of repeats is an
outlier, probably due to one "catastrophic" event with the loss of multiple
repeats (rather than the one-step mutation model). This makes it more like a
unique event polymorphism, and it would be analogous to the DYS455=8 allele that
can be used to classify subgroups in haplogroup I.

There is a way we can distinguish alleles that are IBS vs IBD if we look at
SNPs in the surrounding territory on the chromosome. If an allele is IBD in two
people, then we should see that it's contained inside a relatively long
haplotype block. If an allele is IBS, then it probably occurred on a different
haplotype background. The type of data you got from your deCODEme test would be a
head start in calculating that, but it's rather difficult to extract
haplotypes from genotypes.

Ann Turner




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