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mandag 1. april 2013

Possible application of asymmetries in Chromopainter

I have for some time tried to understand more about the reasons why asymmetries occurs between received and donated chunks in Chromopainter. I have in an earlier post got the understanding that when there are large asymmetries between these it also means they are mutational more distant also meaning more distantly related and opposite if the asymmetries are smaller.

In essence I understand it the way that if the segments are more closely related to each other the more symmetric the segments would be. In a world with no mutations the segments would be identical like in a IBD (identical by descent) analysis and only divided by recombination there would be no asymmetry.

Motivated by a post on another blog called "No Mongolian admixture in Poland" I tried to see if this asymmetries could provide anything of information not only about Poles but to other European populations as well.

First let us look at the CL asymmetries in Europe. The central position of Poles shows that the asymmetrical distances are small only showing some minor deviations to Finns ad Saamis on one side and to French and Romanians on the other.

We can then look at a number of European populations vs Siberian, East-Asian and Native American populations (please note color scales are identical to all):

The tables shows in general that Native Americans and Siberians appears to have smaller asymmetries to Europeans than East-Asians as they appear green while East-Asians who have larges asymmetries appears more in red.

However internally among European populations there is different asymmetries towards these eastern populations. It appears like continental European populations like Poles, French, Hungarians and Chuvash have similar and less asymmetric profiles while northern populations Finns, Saami, Scandinavians and Vologda Russians have similar more asymmetrical profiles. The Romanians also have a similar profiles to the continental Europeans but with even less asymmetries than these towards the eastern populations.

This must be said to be surprising as f.ex Saamis and Vologda Russians especially among the northern European populations appears in absolutte CL terms to have the largest CL shared with these eastern populations.

This may mean that even the sharing are large vs these eastern popuilations it may not mean that the sharing are closer in geneology than with those who share less CL.

As a side note when looking back at earlier posts, the above may explain the positions of some Siberians vs Europeans on MDS plots not close to Saamis or Finns but on the same Y-axis as French and Romanians suggesting similar genetic variations on that dimension.

Little Study of the Saami, Finns and Scandinavians

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