This is the question I get most often when speaking on using DNA for genealogical research. It is impossible to answer the question as stated. Like so many questions, the answer is — it depends.
It depends on
- what you want to learn, and
- whether there is someone alive in the line of interest who is willing to provide a DNA sample.
You should also be aware that taking a DNA test isn't going to knock down all of your genealogical roadblocks. It takes a lot of work to analyze the results and correlate the information with your traditional research to reach a soundly reasoned conclusion.
If you are just curious, I recommend testing as much as you can afford as soon as you can. Your choices are between a Y-DNA test if you are male or can get a male relative to test, a mitochondrial DNA (mtDNA) test, and an autosomal DNA (atDNA) test. An autosomal test usually has a name like FamilyFinder, Relative Finder, or AncestryDNA. Do all of the tests if you are curious and can afford it.
With a Y-DNA test you can learn about the direct paternal line — the tester's father's father's father and so on back through time. You may have an exact match with someone where your common ancestor is many generations back. You can also prove there is no link between the tester and another man.
With an mtDNA test you can learn about the direct maternal line — the tester's mother's mother's mother and so on back through time. You may have an exact match with someone where your common ancestor is many, many, many generations back. You can also prove there is no link between the tester and another person.
With an atDNA test you can learn about all lines of descent, but only back five or so generations. Farther back than that is iffy because of the way DNA is inherited. Two people can be related far back in time, but not show much matching autosomal DNA.
All of these tests may give you clues on how to focus your research to get further back, but you still have to do the traditional research. Each test can provide information to answer focused questions related to genealogy. The Y-DNA and mtDNA tests are available in several different resolutions. In some cases you may only need a low resolution, low cost test. In other situations you may need the highest resolution, higher cost test. But you can't determine which is needed until you know what you want to learn.
Don't be confused by companies who offer kinship tests using the markers used by law enforcement. For Y-DNA, mtDNA, and atDNA genealogical tests check out Family Tree DNA. For atDNA tests, including some information on health-related markers, check out 23andMe. Ancestry.com used to offer all three types of test. It is difficult to find anything on their site now other than the AncestryDNA atDNA test, but be aware they don't yet provide access to your raw DNA data which is absolutely necessary to do detailed analysis.
This will be an ongoing series detailing specific genealogical questions with recommendations for the tests that may help.
To cite this blog post:
Debbie Parker Wayne, "What DNA test do I take? Part 1," Deb's Delvings Blog, posted 9 January 2013 (http://debsdelvings.blogspot.com/ : accessed [date]).
© 2013, Debbie Parker Wayne, CG, All Rights Reserved