Why do you need a DNA test for family history?


20 April 2018
dna-ancestry_2502064b-24330.jpg DNA test
Which family tree DNA test is best? How can a DNA test help with your family history? Debbie Kennett explains why you should have your DNA tested.

Which family tree DNA test is best? How can a DNA test help with your family history? Debbie Kennett explains why you should have your DNA tested.

DNA is now an essential tool for the family historian. It can be used to test hypotheses about relationships and can sometimes provide answers that can’t be found in the paper trail alone.

The databases are growing at a phenomenal rate, the cost of testing has plummeted in the last few years, and DNA testing is now so much more affordable. 

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Which is the best DNA test?

An autosomal DNA test from AncestryDNA, Family Tree DNA or 23andMe can be taken by both males and females and will put you into a matching database to connect you with genetic cousins on all the different branches of your family tree.

Although these tests can provide matches with more distant cousins, they are best used for making connections within the last ve or six generations. It can be very exciting to have genetic con rmation of a genealogical relationship. Some companies will even give you a chromosome browser so that you can see a visual representation of the segments of DNA that you share.

    MORE: 6 ways a DNA test can help you do your family history

If you’re lucky your newly found cousins will also have additional paper records or family photographs and letters to supplement your research and fill in some of the holes on your tree. 

Match genes and surnames

The traditional Y-chromosome DNA and mitochondrial DNA tests can also help with your genealogy research.

The Y-chromosome is passed on by a man to his sons and the transmission usually corresponds with the inheritance of surnames. If you have two males with the same surname a Y-DNA test will tell you whether or not they share a common ancestor. Y-DNA tests can also help with brick walls as a result of illegitimacy or adoption. There are now more than 9,000 surname projects run by volunteer project administrators as well as a range of geographical projects. 

Find distant evidence

Both men and women have mitochondrial DNA, but only women can pass on mtDNA to the next generation, so this test follows an all-female path of inheritance. mtDNA tests are less useful because the surname changes with each generation. It also has a slow mutation rate, which means that the matches can be very distant, but it can be useful in some situations. mtDNA was successfully used in the identi cation of King Richard III’s remains in Leicester in combination with other strands of evidence. 

Which DNA test is best for me?

For Y-DNA and mtDNA, Family Tree DNA is the company of choice. It has the world’s largest Y-DNA and mtDNA databases and the widest range of tests.

For autosomal DNA you can choose between FTDNA’s Family Finder test and AncestryDNA, though many genealogists test at both companies. You never know where you’re going to get the all-important breakthrough match. For health reports as well as cousin matches, you can test at 23andMe.

ISOGG - the International Society of Genetic Genealogy - has a Wiki with lots of useful information as well as charts comparing the services offered by the various companies.

About the author

Debbie Kennett is an Honorary Research Associate in the Department of Genetics, Evolution and Environment at University College London. She writes about genetic genealogy and her Cruwys one-name study on her blog.