Wednesday, 16 March 2011

Progress in genetic genealogy

It's a while since I covered developments in genetic genealogy. There's lots going on, especially with analysis of autosomal DNA, the 22 chromosome pairs we all have, half from father, half from mother.

Each chromosome we get from a parent is a mixture (recombination) of their two corresponding chromosomes. Fortunately the mixture is fairly course, large chunks come from one or other of your parent's chromosomes.

In my own case I have my own and my mother's autosomal DNA analysis done by 23andMe. The test shows conclusively she's my mother, or I'm her son! Our relative ages restricts the possibilities!

The remainder of my DNA came from my father, but from which side of each chromosome pair is unresolved.

My colleague Bryan Cook has been examining a recent paper  “Phasing the Chromosomes of a Family group When One Parent is Missing” in the Journal of Genetic Genealogy , 6(1), 2010, p1-12 by Whit Astley.

Bryan writes that phasing by Whit’s technique, using three or more fully tested siblings and at least one parent, to separate the two sets of SNP bases according to their source chromosomes, opens the door to genealogical applications such as reconstruction of the “missing parent”, identification of grandparents, which side of the family does a new match fit, perhaps further proof of non-paternal events.


Another article in the same issue of the Journal of Genetic Genealogy, by Ann Turner, points out some distinctive features of a region of chromosome six which exhibits considerable variability, but the recombination rate is low. It holds out the possibility of using sections of these more stable chromosomes to look further back in our ancestry than would be expected if the recombination rate were uniform.

We are fortunate to be witnessing the emergence of such DNA techniques for family history that are opening up possibilities unimagined by most of us in the genealogical community only a decade ago.

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