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Every one you can!

There are always a lot of reader questions about what DNA test to take and who to test for the best results for genealogy.

The Legal Genealogist‘s standard answer is: test everyone you can afford to test, with every test that might provide the answer you’re for.

But in case that by itself isn’t helpful, let’s look at specific reader questions and why specific tests might provide solutions to their problems.

Genetic QuestionsQ. Test the older generation?

Reader Walker Hall had a question many people ask: “Since my parents are still around and interested in genealogy, should I skip straight to testing them if they are receptive, rather than waste money on myself? I would assume that as long as they are truly my parents (haha), then my dna results would be of little genealogical value compared to the combination of my parents’ individual results.”

The same question, with a twist, came from reader Diana Bowen: “is it better to go with the older generations in the family when testing? I can get my mom, mother in law, paternal aunt and then my husband’s paternal aunt. Does it make more sense to do this or just to test my husband and me?”

A. Oh, yeah.

This is an easy one. One of the most useful tests for genealogy is the autosomal DNA test — the test for the kind of DNA we all inherit from both of our parents1 in a mix that changes, in a random pattern, from generation to generation in a process called recombination.2 It’s really useful for finding cousins who share some portion of DNA with us with whom we can then share research efforts.3

Because of that recombination in every generation, some DNA that our parents might have inherited isn’t going to be passed on to us. Of necessity, when each parent passes that DNA to us, 50% of what that parent has gets dropped out of the mix. So for autosomal DNA testing, we always want to test any available representative of an older generation: a parent is better than our generation, a grandparent better than a parent.

So Walker should definitely test his parents, and testing both of them will give him all of the possible cousins he might match on either his maternal or paternal side. There isn’t anything Walker can get from testing himself that he won’t get by testing both of his parents.

For Diana, she definitely wants to get testing done by all four of the older generation relatives — but in her case, there is a benefit in testing herself and her husband as well. That’s because, in each of their cases, the older generation candidate on the paternal side is the father’s sister, rather than the father.

Remember that recombination is purely random and it happens not just in every generation but every single time a child is conceived. In Diana’s situation, each father could well have inherited some fairly substantial chunks of DNA that his sister — the aunt — did not inherit. And each father could have passed some or all of those chunks down to his child — Diana or her husband.

As a result, Diana could have cousin matches in the DNA testing databases that her aunt won’t have and her husband may have some that his aunt won’t have. And, of course, the reverse is also true: each of the aunts will match some cousins that their niece and nephew won’t match.

You remember that part about testing “everyone you can afford to test, with every test that might provide the answer”? Yup. I really mean it.

Q. On beyond autosomal?

Diana had another part to her question: “is there any reason to also consider a ydna test anymore (as an extra)?” And reader MC, who’s thinking of getting her whole family tested (including her parents and her brother), was wondering too: “Should I get any of my family members to take the paternal or maternal line tests? What additional data could I expect from those?”

A. Oh, yeah.

This is also an easy one, and again: my answer is yes, do it, and you may learn a lot. Because as wonderful, as exciting, as innovative as autosomal DNA testing is and can be, it often can’t give us a clear-cut answer to the one question we most want to have a clear-cut answer to:

Am I descended from — or at least related to — that one man or that one woman?

For the first question, the answer can come from a YDNA test. YDNA is the kind of DNA found in the male gender-determinative Y chromosome that only men have.4 It gets passed from a man only to his sons and from his sons only to his grandsons and from his grandsons only to his great grandsons, with few changes down the generations.5

For the second question, the answer can come from testing mitochondrial DNA — mtDNA — the kind of DNA we all have that serve as energy producers for the cells in our bodies.6 It gets passed from a mother to all of her children — male and female — but only her daughters can pass it on to her grandchildren.7

I wrote about this back in August in a post called The value of the tests that emphasizes one key fact: those “old tests” are not so “old hat”!8 Being able to nail down a male line or surname or a specific female line of descent can be a powerful addition to genealogical testing, and you can only get this by doing these additional tests.

Bottom line: test everyone you can afford to test, with every test that might provide the answer you’re for.


SOURCES

  1. ISOGG Wiki (http://www.isogg.org/wiki), “Autosomal DNA,” rev. 14 Nov 2014.
  2. ISOGG Wiki (http://www.isogg.org/wiki), “Recombination,” rev. 1 Sep 2014.
  3. See Judy G. Russell, “Autosomal DNA testing,” National Genealogical Society Magazine, October-December 2011, 38-43.
  4. ISOGG Wiki (http://www.isogg.org/wiki), “Y chromosome,” rev. 23 Apr 2014.
  5. Ibid., “Y chromosome DNA tests,” rev. 27 Nov 2014.
  6. What is mitochondrial DNA?,” Genetics Home Reference Handbook, National Library of Medicine, US Department of Health (http://ghr.nlm.nih.gov/handbook : accessed 29 Nov 2014).
  7. ISOGG Wiki (http://www.isogg.org/wiki), “Mitochondrial DNA tests,” rev. 9 July 2014.
  8. Judy G. Russell, “The value of the tests,” The Legal Genealogist, posted date (http://www.legalgenealogist.com/blog : accessed 6 Dec 2014).
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