Sunday, October 28, 2012

DNA in a Nutshell

This blog post is a nutshell version of what you need to know about DNA. Here are the definitions of the three types of genealogy specific DNA tests you can take:

  • yDNA
    This test is for MALES only. yDNA is passed from father to son down the generations with very little change. This test will give you information to follow a single surname back through time and the goal is to find common ancestors with other people. If you are female, you can still take advantage of this by submitting the DNA of your father, brother, uncle or male first cousin with the same surname.
  • mtDNA
    This test can be done by males and females but only females pass mtDNA on to the next generation. Whether a male or a female takes this test, it will follow the maternal line only, mother, her mother, her mother, her mother etc. so it will be crossing a new surname with each generation.
  • Autosomal DNA
    This test can be done by males and females. This one is very different. It looks at your DNA across all lines. The purpose of this test is to link you up with LIVING relatives that you have. The results will tell you who your cousins are (1st-4th are very accurate, 5th-6th are pretty accurate, anything past that is iffy). Of course this test is only able to hook you up with other people that have also taken the test.

Things you need to know:

  • All DNA tests have to be used in conjunction with accurate pedigrees. You will be comparing your family tree with other people that have also done DNA testing.
  • If the surname you are working with isn't one that has had a lot of DNA testing, you won't have near as much success as with those surnames that have had a lot of testing done, HOWEVER, you still want you get your data out there because as time goes by, more and more people will be getting tested and you will start having connections.
  • You can join surname projects where everyone with the same surname is put into a database that compiles the data and compares/contrasts it to help you find matches and to help separate all of the different lines that have the same surname.

The top three DNA companies are:

  • Family Tree DNA
    This company does all three tests.
  • 23 and Me
    They do autosomal DNA only (they also do medical DNA testing but autosomal is the only one they do that is genealogy specific).
    Ancestry does all three tests but their autosomal test is still in beta testing. Ancestry does not release their raw data which means you can't take your results to another company and plug into their databases. This is a major drawback. There are rumors that Ancestry is planning to allow the release of the raw data in the future. We shall see.

Here is one that is still in beta testing that is a bit different but still very interesting. It is put out by the National Geographic Society. It is a combo yDNA and mtDNA test (woman would only get the the mtDNA part so they should have a close male relative take the test for them). They do not release the raw data but say on their website that they are planning to do so. Their emphasis seems to be on origins and migration more than genealogy. This is a big research project where the results will eventually be published (in the public domain). They do have a partnership with Family Tree DNA. I am not sure if this is one that genealogists would be as interested in but if they will take raw data from other companies it might be worth getting involved in this project.

To get a more comprehensive education about DNA, I encourage to to watch the two FREE webinars by DNA expert Ugo Perego:

The Family History Library has a FREE course on yDNA specifically:

Relative Roots has Four DNA webinars:

Copyright © 2013 Michele Simmons Lewis


  1. Today whether it is about paternity testing or any other criminal activity, DAN testing is acceptable as a most effective proof in all judicial system. Even in stem cell therpy also it has an effective role. Thank you very much.

  2. DNA has so many uses today. Yesterday my daughter came home and told me that a rep from some DNA company visited their office. She works for a large cardiology group. The rep was telling them that their company takes DNA samples and tests for the potential for certain diseases and medical conditions. They swabbed one of the doctors. They will get back with the doctor and let him know the findings. This is a bit scary to me. If you will be getting some incurable illness sometime in the future would you want to know? I am not sure about that.