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Archiver > GENEALOGY-DNA > 2009-05 > 1241807532


From: "Ken Nordtvedt" <>
Subject: Re: [DNA] Not all clusters are created equal
Date: Fri, 8 May 2009 12:32:12 -0600
References: <663166.2235.qm@web24504.mail.ird.yahoo.com>


Particularly in the autosomal dna there could be a bunch of clines which
don't rise to the level of clustering. Nevertheless, one can navigate via
the genetics to some degree of accuracy using one's position in a bunch of
clines.

----- Original Message -----
From: "Anders Pålsen" <>
To: <>
Sent: Friday, May 08, 2009 12:15 PM
Subject: Re: [DNA] Not all clusters are created equal



So we need an "abrupt" finding in an else "continous homogenous"
geographical area to be sure it represent an actual cluster? Could the Sami
population be a hot canditate in Europe?

Anders


--- Den fre 2009-05-08 skrev Vincent Vizachero <>:

> Fra: Vincent Vizachero <>
> Emne: Re: [DNA] Not all clusters are created equal
> Til:
> Dato: Fredag 8. mai 2009 14.53
> On May 3, 2009, at 11:19 PM, argiedude wrote:
>
> > But identifying a genetic cluster doesn't
> automatically mean it
> > represents an ancient population cluster.
>
> It is also worth remembering that identifying a genetic
> cluster in a
> sample does not mean you've identified a genetic
> cluster in the
> population.
>
> It is common in studies to genotype a number of individuals
> from
> distinct populations. If these populations are
> sufficiently separated
> from each other, and no intermediate populations are
> sampled, they
> will appear as distinct "clusters" in PCA or MDA
> plots. A recent
> paper
> (http://dienekes.blogspot.com/2009/05/genetic-structure-in-europeans-nelis-et.html
>
> ), for example, sampled two Italian populations (among
> many
> others): one from Piemonte and another from Apulia.
> Unsurprisingly,
> when analyzed these two populations were distinguishable
> for most
> sampled individuals.
>
> It would be easy, but misguided, to describe these two
> samples as
> population "clusters" but they are really not
> that. Sampling the
> 800km distance at, say, 50km intervals would reveal that
> genetic
> variation in Italy is gradual and continuous. Picking the
> two points
> displays a discreteness that picking more points would
> reveal to be
> an mirage.
>
> I bring this up in large part because it is common for
> readers of
> these papers, or customers of full genomic scan services
> (like
> 23andMe) to think in terms of belonging or not belonging to
> certain
> genetic clusters when (in fact) the clusters are merely
> artifacts of
> the study design.
>
> VV
>
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