Wednesday, May 17, 2006

mtDNA 101

Whether you are male or female, your mitochondrial DNA is inherited from your mother, who inherited her mtDNA from her mother, who inherited her mtDNA from her mother, ad infinitum (well, maybe not infinity, but at least ad nauseum).    It is passed from a mother to each of her children, male and female, but never inherited from the male, as illustrated by this Chart.

Thus, when you test your mtDNA you are testing your matrilineal ancestors (perhaps ancestresses?).   Corroborating such testing by traditional genealogy is considerably more difficult than corroborating your patrilineal ancestors, in part because of the surname change each generation, but also in part because of the legal status of women in many societies in the past and the fact that records were kept primarily by men for men.

mtDNA is tested on a sequence of two separate regions of the mitochondrion.   The first region is called Hyper-Variable Region 1 (HVR-1 or HVS-I), positions 16000 through 16569.   The second region is called Hyper-Variable Region 2 (HVR-2 or HVS-II), positions 1 though 575.   Most labs test some portion of either or both of these regions.   This result is then compared to a reference sequence, the Cambridge Reference Sequence, and any differences are reported.   Berry mtResults.   An exact match between two people indicates that they share a common ancestor.   However, since mtDNA mutates extremely slowly this common ancestor could have lived thousands of years ago.

The least expensive mtDNA test I have come across is offered by Argus BioSciences.   It tests the entire mitochondrial D-loop region which includes base pairs 16000 to 16569 and 00001 to 00575, a total of 1145 base pairs including the full hypervariable regions I & II, all for only $99 now $75.


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