XDNA: Not As Mysterious As It Sounds
How to use your XDNA results for genetic genealogy, whether you’re a man or a woman. Sort your DNA matches using XDNA and rebuild your genetic family tree!
We usually talk about THREE kinds of DNA tests available for genealogists: YDNA, mtDNA, and autosomal DNA. However, there is a fourth category of DNA that can prove useful in your genetic genealogy searches. It can’t be tested on its own, but is produced as part of an autosomal DNA test. It is the XDNA.
What is XDNA?
YDNA and XDNA determine our gender. Men have one XDNA from their mom, and a YDNA from their dad, while women have two copies of the XDNA, one from each parent. Because of this association of the XDNA with a man’s mother’s side, it is often confused with the mtDNA, which is ALSO associated with our mothers.
However, these are two very different kinds of DNA with very different inheritance patterns. The mtDNA is passed from a mother to all of her children, and then only the females pass it to the next generation. For this reason, the mtDNA you have is the same as your mother’s and your 10X-great grandmother’s (which still blows me away every time I think about it!).
The XDNA, on the other hand, has a very tricky inheritance pattern. Here’s what it looks like for women (the orange boxes in the fan chart are the female ancestors, and the green are the males):
And here’s what it looks like for men:
While all companies are testing XDNA, only two companies, 23andMe and FTDNA, report XDNA results. At Family Tree DNA, they even allow you to filter your results by those matching your XDNA:
You can also see XDNA results by transferring to GEDmatch. As shown below, you’ll see your XDNA matches along with information about how much DNA you share.
XDNA testing for men v. women
Because a man receives XDNA only from his mother, his father’s side of the pedigree is completely blank. This actually helps XDNA match analysis in many cases for men, as any match who is sharing XDNA should only be related on the maternal side, providing an easy way to identify maternal side matches. (But be careful, as not all matches on a mom’s side will share XDNA with you.)
Women, on the other hand, are more complicated. Since they receive one XDNA from each parent, they have XDNA from ancestors on both sides of their pedigree chart.
While XDNA might be slightly more useful for men, it is still very useful for women. Looking at the charts again you can see that there are a lot of white spaces for both men and women. Looking at the white spaces on an XDNA match’s fan chart will immediately tell you all the ancestors that DO NOT connect you and your match, leaving only a handful of ancestors that could be connecting you.