|My maternal grandfather, Louis Allen Shepherd, with his mother Katherine Sheppard/Shepherd.|
Hopefully, this DNA test will get us a little (or even a lot) closer to finding an answer. The AncestryDNA test (through Ancestry.com) is an autosomal test. Normally when we (non-scientific, lay people) think about DNA and chromosomes, we think about the sex chromosomes: xx for women and xy for men. But humans actually have 22 other pairs of chromosomes called autosomes - these basically program us for all the things aside from our sex. The autosomal DNA test analyzes these chromosomes and then compares them to others in the company's database (note Ancestry isn't the only company that does this kind of test, and so different companies have different databases of varying sizes). The results they give you will tell you 1) the geographic regions of the world where it's likely your ancestors came from, and 2) if there are people in their database of other test-takers who are likely to be related to you. (Only people who wish to be identified are identified.)
According to International Society of Genetic Genealogy, autosomal DNA tests are highly accurate up to the second cousin level, meaning that this should be able to link my uncle to people who would have the same great-grandfather as him. We're just hoping we'll find someone who shares the same grandfather as him!
I may also ask my mom and her other siblings to take the test, recognizing that each child inherits only a selection of their parents' genes. Each child gets 50% of their DNA from each of their parents, but which genes? The more of Louis' kids who take the test, perhaps the more luck we'll have with our ancestor search, because we will have a broader base of their dad's DNA - the matches from Ancestry's test-taker database that they have in common will seemingly be our best bets for finding a common ancestor. (Their mother's family is well-documented, so it should be relatively easy - no pun intended! - to separate known family from new discoveries.)
So, here's hoping we have some luck!
P.S. I am NOT an expert on genetic genealogy - I'll be learning as we go along. Credit where credit is due: I have to thank Gina Paige of AfricanAncestry.com for teaching on this topic several times at meetings of the African American Genealogy Group (AAGG) in Philadelphia, as well as Dena M. Chasten-Ellis of the African American Historical and Genealogical Society - Delaware Chapter for doing the same. And I keep coming back to the International Society of Genetic Genealogy Wiki when I need more information or a refresher.