GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2008-12 > 1229208228
From: "David Faux" <>
Subject: Re: [DNA] X Chromsome Block Party - Potentially as Informative asmt and Y DNA
Date: Sat, 13 Dec 2008 14:43:48 -0800
There are four "blocks on the go" at the moment - at dna-forums.
Kathy has flagged two.
Here is a link to one that I located near the centromere in a region that is
highly conserved - so much so that there are only 3 haplotypes discovered in
a 5 million base segment of 24 SNPs (wedged between two genes) so far, but
many with SNP changes (unlike what is typically seen in haploblocks along
the arms of the X).
The output of another haploblock, which I chose because the decodeme browser
said that it is almost exclusively found in Asians is a string of
34 SNPs embedded in a matrix of 600,000 bases. Here is the URL (first draft
only as is the above):
While a Turkish idividual matched me 34/34, so did someone with materal
ancestry in southern France. There are three times as many haplotypes
as seen in the above and they are considerably more variable suggesting that
a great deal more crossing over behavior has influenced these markers in
hitching a ride.
Anyway, something to ponder - it will be at least two months before I can
get up to any sort of "speed" via reading the literature and learning how to
use a program called PHASE. Anders and Ann have a great head start in this
so I am going to use the sprinting skills that were identified by 23andme
and see if I can forge ahead at a rapid pace (being retired will help
David K. Faux.
On 12/13/08, <> wrote:
> > I'm wondering about X-block size.
> > Too big and the information might be
> > "blurred" across population groups?
> > Too small and it may be highly
> > conserved over many population groups
> > and thus not very useful <snip>
> As it turns out, many of the blocks are quite useful.
> The size is much larger than the block sizes we are
> seeing because there appears to be a string of unique
> event polymorphisms that 23andMe reports on each of us
> representing a much larger block. So what they have
> done is "tagged a neighborhood" to quote a deCODEme
> I seem to match other people in my first reported block
> who have English ancestry. But if you look at the
> immediate block preceding it, there is another block
> which probably represents another origin. Some of us
> differ primarily at the first four markers. If those people
> take the first four markers in this block and look at
> the preceding 25 markers, you may find a completely
> different match that can be predicted from just 4 markers.
> For example if you take these 4 markers and add to the
> 10 preceding markers you may have another match,
> but with someone from Finland instead of England.
> I start with GAAC, but others start with GGAC or
> AGCA etc.
> We inherit many blocks from several ancestors all
> spliced together.
> I wish more people would now report on the preceding
> 25 markers represented by this link to
> 23andMe, Version 2:
> Unlike the next page of 25 markers, the second position will be a
> C or T to be able to distinguish the two sets, e.g.. GCACG etc.
> Here is the link to the markers we first started out with which is
> the contiguous block coming after the block above.
> I also started a discussion in General DNA discussions at DNA-Forums
> for people who just want to learn more about the X chromosome and
> the inheritance of it. It is truly fascinating to follow these blocks.
> We have several discussions going in the 23andMe section.
> Kathy J.
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