Q. I’ve had autosomal DNA testing done for my father, mother, wife and myself. We’re awaiting the results for my brother’s test. I transferred the Ancestry DNA results to GEDmatch and Family Tree DNA. Whom should I test next?
A. The autosomal DNA test traces both sides of your family tree and is helpful in researching the most recent five or six generations. The more distant the ancestor, the less of that person’s DNA you have until he or she “drops off” your genetic family tree altogether.
The most basic rule in autosomal DNA testing is to test any relative who doesn’t have both parents living, starting with the oldest generations. But since most of us don’t have the financial resources this approach might require, a testing plan also should take into consideration the reasons for pursuing genetic genealogy. More often than not, test-takers are in one (or both) of two situations:
- they’re trying to solve a family history mystery
- they just want to see what they can find out
Your DNA Testing Strategy for Solving a Family Mystery
If you have a family tree mystery, create a testing plan that will maximize your chances of finding out more about the ancestor in question. Set your sights on descendants of the mystery ancestors who are from lines other than yours.
Say you’re trying to find the parents of your mom’s dad’s mom—your great-grandmother—Jane Lewis. You carry about 12 percent of Jane’s DNA (you have 50 percent of your mom’s DNA and 25 percent of your grandpa’s), and only about 6 percent of the DNA of each of her parents, the people you’re trying to find.
To find out more about Jane’s parents, you need more DNA. Testing any of Jane’s descendants is helpful. But most helpful will be testing your second cousins, people who are descended from Jane’s other children—your grandfather’s siblings. These siblings got different parts of Jane’s DNA than your grandfather did, and passed some of those parts down to their children and grandchildren.
Testing a second cousin also lets you differentiate the DNA you received from Jane (and her husband; we can’t separate the two at this point) from the DNA you received from your seven other great-grandparent couples. You can do this by studying the matches you share with your cousins using the Shared Matches, In Common With or similar tool offered by your testing company.
In that list of shared matches, look for third cousins who might be descended from Jane’s parents or fourth cousins who might be descended from Jane’s grandparents.
Your DNA Testing Strategy for Seeing What You Can Find Out
If you’re testing not to address a particular question, but just to see what you can find out, try this:
- Test second cousins from each of your known great-grandparent lines, starting with older relatives.
- Consider finding a direct paternal line descendant of each of your four great-grandfathers to take a Y-DNA test, which would represent the surnames of each of those lines. The Y-DNA record for these paternal lines can help you sort out how other lineages with the same (or similar) surnames are related.