GENEALOGY-DNA-L Archives
Archiver > GENEALOGY-DNA > 2008-12 > 1230335004
From: Anders Pålsen <>
Subject: Re: [DNA] How "African" block (rs4827539 - rs2497944) gotintotheWestern Europea
Date: Fri, 26 Dec 2008 23:43:24 +0000 (GMT)
In-Reply-To: <ea3bd9560812222318v5b0e7e3bm4253c409a117d7af@mail.gmail.com>
It seems so far that the easiest read in your collection is the first article:
http://www.broad.mit.edu/~sfs/nrg_Xchrom.pdf
Some useful information:
1. Recombination rate 0.8 cM/Mb (autosomes 1.1)
2. Mutation rate 0.015 per megabase
3. Two thirds of x-chr from females.
4. Age 750 000 years.
The last one is interesting, do this mean that we may find some very old x-chromosome blocks from interbreeded before the oldest known mtDNA and y-chr age estiamtes?
Further they confirm that the X-chromosome may be provide more information than the single locus the Y-chr and mtDNA havem, quote:
"Second, there is the presence of recombination. If
ease of haplotyping distinguishes the X chromosome
from the autosomes, it is the occurrence of recombination
that distinguishes it from the Y chromosome and
mtDNA. In the latter two systems, the entire chromosome
acts as a single locus and shares a single genealogical
history. The X chromosome and the autosomes, on
the other hand, are broken up by recombination at
every generation, so that different regions have different
histories. This difference has important implications for
historical investigations. In practical terms, recombination
makes it harder to study phylogenetic trees and so
X chromosome-based phylogenies must be restricted to
regions with very strong LD. In broader terms, however,
recombination creates a tremendous resource: it means
that the X chromosome records hundreds or thousands
of different snapshots of the population’s history,
whereas the Y chromosome and mtDNA each record
only a single one. Because the history of any single locus
only crudely records the history of the population in
which it lived (see BOX 3), information from a recombining
system is crucial for providing as complete a view as
possible of the history of human populations. It is the
combination of accessible haplotypes and multiple
genetic histories, therefore, that makes the X chromosome
a uniquely powerful tool for historical studies."
Anders
--- Den tir 2008-12-23 skrev David Faux <>:
> Hello Anders:
>
> Here is a reference list where at least four of these
> articles (including
> the one I noted in an earlier post) speak to your question.
> I must note
> that this is only a draft but it does include a number of
> good references.
> What strikes me is the relative lack of recent articles
> focusing on the X,
> most are found from 1997 to 2004. I suspect that I have
> missed a few
> important references. If someone is aware of an article
> that should be
> included, I would appreciate the URL. Thanks.
>
> http://davidkfaux.org/X_CHROMOSOME_Haploblock_Resources.pdf
>
> David K. Faux.
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