XDNA: Not As Mysterious As It Sounds

Diahan Southard

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XDNA can be used for genealogy, whether you’re a man or a woman. Sort your DNA matches using XDNA to help you with your family history.

XDNA genealogy family history IO.png We usually talk about THREE kinds of DNA tests available for genealogists: Y DNA, 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.

Two DNA testing companies report XDNA information: Family Tree DNA (the Family Finder test)* and 23andMe. Check out this quick video tutorial and the article below.

 

What is XDNA?

XDNA.jpg Y DNA and XDNA determine biological sex:

  • Genetic males have one XDNA from their mom, and a YDNA from their dad.
  • Genetic females 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 both women and men (the orange boxes in the fan chart are the female ancestors, and the green are the males):

XDNA inheritance pattern for a woman 

XDNA inheritance pattern for a man

What testing companies report XDNA?

While all companies are testing XDNA, you’ll only get XDNA reports from two tests: 23andMe and FTDNA’s Family Finder test. At Family Tree DNA, they even allow you to filter your results by those matching your XDNA:

FTDNA+XDNA.jpg

You can also see XDNA results by transferring to GEDmatch, although the site is not something I generally recommend. As shown below, you’ll see your XDNA matches along with information about how much DNA you share.

GedmatchXDNA.jpg

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.

Mentoring-01.png If you would like help figuring out how to make heads or tails of your XDNA matches, schedule a Your DNA Guide Mentoring session. We can help you!

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<a href="https://www.yourdnaguide.com/author/guideyourdnaguide-com" target="_self">Diahan Southard</a>

Diahan Southard

As founder and CEO of Your DNA Guide, Diahan Southard has been teaching people how to find family history answers in their DNA for several years, and she's been in the genetic genealogy field since its infancy. Diahan teaches internationally, writes for popular magazines, consults with leading testing companies, is author of Your DNA Guide–The Book, and producer of Your DNA Guide–the Academy, an online learning experience.

6 Comments

  1. Margaret Champion

    I think the xDNA can be helpful. I will have to examine further. And, since the test has already been done if you did FF, there is no extra cost! Thank you for explaining this!

    Reply
  2. D

    Interesting!

    Reply
  3. Patricia Nikkila

    Why do you not recommend Gedmatch site? Thanks.

    Reply
  4. Patricia Lange

    FamilyTreeDNA was the second site I tested at. (The first was the National Geographic site.) At the time, there was no “Family Finder” feature and I think it just did YDNA and mtDNA testing. I was pleased to finally learn here what the X Match meant and to try out that feature. Lo and Behold I had multiple matches, but only one of them had a shared DNA over 11 cM. I already knew her and have her in my tree. Does this mean the X DNA feature is of no use to me?

    Reply
    • Danielle Francis

      Hi Patricia, our rule of thumb is that matches should share at least 10 cM on the X chromosome to be useful in finding connections. The good news is that new people are joining DNA testing databases everyday, so you never know when a new XDNA match will show up on your match list. I would recommend working on another line for a while anc checking back in on your XDNA in a few months to see if anyone new has come up.

      Reply

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