Wednesday, May 25, 2011

Decoding an Ancestor's Y-Chromosome DNA Signature


In this blog on May 4th, I reported on my first Y-chromosome match (a non-Dowell) using 111 markers for comparison. Now, results from two other Maryland Dowells are beginning to trickle in. One of them, Barry, is a 6th cousin-once removed and he was an exact 67 marker match with me. We are now exact 93 marker matches with 18 of his markers remaining to be reported. We hope those 18 are reported within the next week. Another Dowell, Mark, a seventh cousin-once removed, also has the same additional 26 markers back and he agrees with Barry and me on these 26 newly reported markers. However, he differs with Barry and me on two markers over the first 67.

Within the next few weeks we expect the remaining results for Barry and Mark and the complete 68-111 marker results for two other cousins. One of them, Ron, is a sixth cousin of mine and an exact 67 marker match so far with Barry and me. The other, George is a sixth cousin-once removed who is 63/67 match with Barry, Ron and me. These additional results will allow us to triangulate the markers back to our earliest known Dowell ancestor who was Philip Dowell, Sr., who died in southern Maryland in 1733.

Mark descends from Philip, Sr.’s first son Philip, Jr.
George descends from Philip, Sr.’s second son John.
Ron, Barry and I descend from Philip, Sr.’s third son Peter.

So far it appears that we can calculate Philip, Sr.’s first 93 markers. Four descendants of son Peter are exact 67 marker matches of each other. One descendant of son Philip, Sr., matches them on 66 of those 67 markers. Mark also shares that mismatch. However, on the marker on which the descendants of Philip, Jr., differ from the descendants of Peter, George and one other descendant of son John have the same marker value as do the descendants of Peter. So it would appear that the four descendants of Peter have not had any mutations over the generations down from Philip Dowell, Sr., on markers 1-67. There is unanimity on the values on markers 68-93 among Barry, Mark and me. Therefore, it appears that we now can reconstruct the values of the first 93 markers of Philip Dowell, Sr., who was buried in 1733. That's good because we don't know exactly where his body was buried.

If you have followed all this, you really haven’t been paying close attention.

I would appreciate any critique, correction, comment or question. 

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