XDNA: A Case Study

Diahan Southard

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This XDNA case study shows how XDNA may give you clues about how you’re related to your DNA matches and who your common ancestor might be.

Trying to use autosomal DNA to identify ancestral connections further back than 3X great grandparents can be tricky (at best). I don’t recommend it for most genetic genealogists, especially if you are just starting out. But if you are going to brave these turbulent waters of distant connections with small pieces of DNA, XDNA offers a great supplementary strategy.

That is because of XDNA’s unique inheritance pattern that may allow pieces of DNA to last longer in our families than other kinds of autosomal DNA.

So how does this play out in actual research? Here’s an example.

XDNA case study

Not long ago, we shared an inspiring story about descendants who are trying to reconstruct their shared family tree. One of the researchers, Judy Hughes, is exploring a genetic connection with Helen, who descends from a family that was enslaved by Judy’s ancestors.

Helen says she met Judy after Judy saw her family tree at Ancestry.com. “She was researching my third great grandfather Henry (Harry) Worke, who’d been manumitted [from slavery] in 1809, at the age of 10, in the North Carolina will of Colonel Alexander Worke, who also freed Henry’s mother and his aunts and uncles.”

“Henry’s wife, Rachel, with whom he had 10 children, was enslaved, as was Rachel’s mother Dicey and all of Rachel and Henry’s 10 children. They were enslaved by the Torrence family.”

The Torrence family are ancestors of Judy. Judy wonders whether she and Helen share a common ancestor, specifically Alexander Torrence, her 3x great grandfather and the brother of Margaret, whose 1842 will lists Henry and Rachel as enslaved people.

Judy and Helen are not autosomal DNA matches. This doesn’t preclude them from being related, though. Evidence of shared autosomal DNA can disappear within three or four generations. Interestingly, Helen and Judy’s first cousin ARE autosomal DNA matches. Helen and Judy DO share a small segment of XDNA.

Distant autosomal connections and small XDNA segments aren’t the most confidence-inspiring DNA evidence to work with. But where paper trails fail to exist, sometimes that’s all you have to work with.

Luckily for Judy and Helen, they are in a position to use XDNA to investigate a possible shared ancestor in Alexander Torrence. See, if Alexander is their shared ancestor, then XDNA inheritance patterns indicate that they COULD have both received XDNA from Alexander, based on where he fits on each of their family trees:

Helen XDNA.png                        Judy XDNA cropped.png

As it turns out, Judy’s half-sister Amy has also taken a DNA test, and it turns out that Amy and Helen do share XDNA. Because Amy has the same XDNA inheritance pattern as Judy (being half-sisters), this sharing is possibly due to common descent from Alexander Torrence.

Now, keep in mind their connection would have been a very long time ago, and their shared piece of XDNA is very small (and there are some other XDNA shenanigans that we didn’t get into but that make us feel a little unsure about pinning this shared segment to Alex). Just as in other genetic genealogy cases, this shared XDNA adds just a bit more evidence that they are on the right track with their genealogical paper trail.

What’s the point of this story? I can think of two take-homes:

  1. First, XDNA can be powerful. When the inheritance pattern fits, it can provide clues to help narrow the possibilities of how you might be related to someone.
  2. It’s so important to invite multiple family members to take DNA tests! Each family member tells their own part of YOUR DNA story. In this case, Helen’s results and Amy’s results both provide important (if subtle) clues about the nature of their intertwined genetic relationships.

More resources to find your ancestors

We are continuing to develop more resources to help you understand and navigate your DNA matches. Be sure to check out our free guide on other ways you can use DNA to find your Ancestors .

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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.


  1. Chris Schuetz

    Beth? She’s not in this post, nor the earlier one.
    Are you just trying to see if we have been paying attention? Or is there more to this story? If so, love to read it.

  2. Diahan Southard

    Thanks for your question, Chris. Sure, we were just testing you….No, just kidding. Beth is one of many more cousins who is part of this story, but we accidentally mentioned her instead of Helen. We’ve corrected the name. And I’m glad you’re enjoying this story! We do hope to tell more of it in the future.

  3. Diane Bland

    So, it is suggested you can’t go beyond the 3times great grandfather because of too little DNA? I’m trying to find a Smith family at the 4times Great grandfather and a Green at the same generation. I can line up the Green, but don’t know how to find the next generation. Help.

    • Your DNA Guide

      Hi Diane – At that 3rd or 4th great grandparent level, you are reaching the boundaries of where autosomal DNA can be helpful because you might not have inherited any DNA from that ggg-grandparent. If you’re looking that far back, make sure you test all your siblings and then create a targeted testing plan to really hone in on that ancestor. If you can, YDNA would be much more helpful in that search!


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