Tag: BGA

Me, myself, and Myanmar

By Razib Khan | January 11, 2011 3:22 am

I have spoken of my somewhat atypical, for a South Asian, genetic results before. Recently Dienekes performed some cluster analysis which confirmed the initial findings, while adding a little detail:

I am DOD075. The Southeast Asian component is modal in Malays, while the East Asian component is modal in the North Chinese. Vietnamese and Cambodians are mixed, with the former biased toward East Asian, and the latter Southeast Asian. My own proportions are more balanced, but there might be some noise in there. That being said, from what I have read of Southeast Asia it is highly likely that Burmese ethnicities will be between the Cambodians and Vietnamese in proportions. The Burmans were more shaped by the indigenous Mon-Khmer people than the Vietnamese were, though like the Vietnamese they seem to hail from southern China. My family is traditionally from eastern Bengal, and has been at various points the subjects of the kingdom of Tripura.

Here’s the Dodecad Indians, HapMap Gujaratis, and Behar et al. North Kannadans. The orange is Asian. Can you tell which one I am?

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CATEGORIZED UNDER: Genetics, Genomics

Eurogenes 500K SNP BioGeographicAncestry Project

By Razib Khan | November 23, 2010 12:11 am

Since I have been promoting the Dodecad Ancestry Project, it seems only fair to bring to your attention Eurogenes 500K SNP BioGeographicAncestry Project. The sample populations are a bit different from Dodecad, but again ADMIXTURE is the primary tool. But the author also makes recourse to other methodologies to explore more than simply population level variation. For example, his most recent post is Locating and visualizing minority non-European admixtures across our genomes:

Imagine, for example, a white American carrying a couple of tiny segments of West African origin, from an ancestor who lived 250 years ago, and an eastern Finn with no Asian ancestors in the last 4000 years or more. If we run an inter-continental ADMIXTURE analysis with these two, it’s very likely the American will score 100% European, while the eastern Finn will probably come out around 9% North and East Asian due to really old Uralic influence.

That sort of thing isn’t a huge problem when comparing the genetic structure of populations. Obviously, overall, eastern Finns rather than white Americans are genetically closer to North Asians, and that’s basically what ADMIXTURE picks up. However, if the focus is also on individuals, this certainly can become an issue. Our hypothetical American might be aware of that African ancestor, with solid paperwork backing up their genealogical connection, but he’s pulling his hair out because nothing’s showing up via genetic tests.

So let’s take a look at a real life example of how RHHcounter can pick up segments of potentially recent Sub-Saharan African origin…

euras1
Olivia Munn & Uyghur woman

The basic issue here is that in terms of genomic variation old admixture looks different from new admixture. Someone who is a first generation Eurasian, with a Chinese and European parent, may be about the same ancestral mix proportionally as a Uyghur. They would resemble a Uyghur on STRUCTURE and be placed within that cluster on a PCA chart (this is what happens in 23andMe). But, the Uyghur “Eastern” and “Western” genetic heritage has been reshuffled to a great extent by recombination over the past 1,000-2,000 years. In contrast, a first generation Eurasian will have huge swaths of their genome which are Eastern or Western on alternating strands (from their respective parents). In population genetic language a group of first generations hybrids would be exhibit a lot of linkage disequilibrium (LD). In a panmictic hybrid population LD will decay due to recombination, which breaks apart the distinctive allelic associations inherited from the parental populations.

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CATEGORIZED UNDER: Genetics, Genomics
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This blog is about evolution, genetics, genomics and their interstices. Please beware that comments are aggressively moderated. Uncivil or churlish comments will likely get you banned immediately, so make any contribution count!
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