Using DNA Testing for Genealogy
Basic information about the types of DNA tests that can be used for genealogy
DNA testing can be a valuable clue in determining who your ancestors were. There are 3 types of commercial DNA tests for genealogy and each has specific uses and limitations.
Autosomal DNA testing
Autosomal DNA testing tests a broad spectrum of your DNA and can give you a list of matches to others who tested at that same company that are related in any line of your tree. Autosomal testing is currently offered by Ancestry.com, MyHeritage.com, FamilyTreeDNA.com, and 23andMe.com. (GedMatch.com, MyHeritage.com, and FamilyTreeDNA.com accept transferred tests from other companies.)
The limitation of autosomal DNA testing is that it's generally only useful within your first 4-5 generations or so. Beyond this, you are using very small segments of DNA and it can be easy to make errors and assumptions that may not be correct.
Note that ThruLines, Theory of Relativity, and other tools that DNA companies have available are simply the best estimate of how you may be related based on how other users of the site have built their trees. Any theory that you have about how you are related to someone else should always be backed up by solid genealogy research and source documents.
Y-DNA testing measures a part of the DNA that is passed from father to son. It can help you narrow down specifically to just one line of your family which would be helpful in identifying a man's father. It has to be taken by a direct male descendant of the ancestor you are focusing on. For example, if I'm trying to find the father of my ancestor James Brown, I would need someone to take a Y-DNA test who carries the Brown surname and comes through the son of James, through a son of James's son, through a son, through a son, etc, down to the present. If you are not descended from the particular ancestor in your tree in that way, you can find a cousin or other relative to take the test for you.
Y-DNA testing has the advantage of being able to help identify information going back for many generations, but interpreting the results can be more complicated. For more information about Y-DNA testing see our article about Y-DNA testing.
Y-DNA is currently only offered through FamilyTreeDNA.com.
Mitochondrial DNA (mt-DNA)
Mitochondrial DNA is a part of the DNA that is passed from a mother to her children. It can help you to narrow down specifically to just one line of your family in the maternal line, the line from your mother, back to her mother, to her mother, etc. If you are not descended from the particular ancestor in your tree in that way, you can find a cousin or other relative to take the test for you.
Mitochondrial DNA testing has the advantage of being able to help identify information going back for many generations, but interpreting the results can be more complicated.
Mitochondrial DNA is currently only offered through FamilyTreeDNA.com.
Resources for Learning More
Using DNA testing for genealogy purposes can be quite complex so learning as much as you can on the subject will help you to use your test results effectively. Here are some excellent resources for learning more:
Need help finding more records? Try our genealogical records directory which has more than 1.3 million sources to help you more easily locate the available records.
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