I recorded the video, Understanding X-DNA Inheritance, for the FamilyTreeDNA RootsTech booth to help you understand what X-DNA is, how it’s inherited, and why it’s uniquely useful.
FamilyTreeDNA is the only genetic genealogy company to include X-DNA matching with your autosomal test results, and it’s free.
X-DNA is a powerful tool with a unique inheritance path for males and females that can help confirm or eliminate genealogical relationships within your Family Finder results.
You can watch the video for free on the RootsTech website, here, or on YouTube, here. It’s short, just 17 minutes, but packed full of good information.
Unfortunately, X-DNA is often confused with mitochondrial DNA, but it’s not at all the same. I wrote about the difference in the article X Matching and Mitochondrial DNA is Not the Same Thing.
You can also read more in the article, X Chromosome Master Class, here.
Take a look and see how X-DNA matching can give your genealogy a boost if you take a Family Finder test or transfer a DNA file to FamilyTreeDNA from another vendor.
Enjoy!
_____________________________________________________________
Share the Love!
You’re always welcome to forward articles or links to friends and share on social media.
Subscribe!
If you haven’t already subscribed, it’s free. You’ll receive an e-mail whenever I publish by clicking the “follow” button at the top of the main blog page, here.
Help Keep This Blog Free
I receive a small commission when you click a vendor link in my articles and purchase that item. This does NOT increase your price but helps me keep the lights on and this informational blog free for everyone. Please click on the affiliate links in the articles or to the vendors below if you are purchasing products or DNA testing.
Thank you so much.
DNA Purchases and Free Uploads
- FamilyTreeDNA – Y-DNA, mitochondrial and autosomal DNA testing
- MyHeritage DNA – Autosomal DNA test
- AncestryDNA – Autosomal DNA test
- AncestryDNA Plus Traits
- 23andMe Ancestry – Autosomal DNA only, no Health
- 23andMe Ancestry Plus Health
Genealogy Products and Services
- MyHeritage Subscription with Free Trial
- Legacy Family Tree Webinars – Genealogy and DNA classes, subscription-based, some free
- Legacy Family Tree Software – Genealogy software for your computer
- OldNews – Old Newspapers with links to save to MyHeritage trees
- MyHeritage Omni comprehensive “everything included” subscription plan
- Newspapers.com – Search newspapers for your ancestors
- NewspaperArchive – Search different newspapers for your ancestors
My Books
- DNA for Native American Genealogy – by Roberta Estes, for those ordering the e-book from anyplace, or paperback within the United States
- DNA for Native American Genealogy – for those ordering the paperback outside the US
- The Complete Guide to FamilyTreeDNA – Y-DNA, Mitochondrial, Autosomal and X-DNA – for those ordering the e-book from anyplace, or paperback within the United States
- The Complete Guide to FamilyTreeDNA – Y-DNA, Mitochondrial, Autosomal and X-DNA for those ordering the paperback from outside the US
Genealogy Books
- Genealogical.com – Lots of wonderful genealogy research books
- American Ancestors – Wonderful selection of genealogy books
Genealogy Research
- Legacy Tree Genealogists – Professional genealogy research
Share this:
Discover more from DNAeXplained - Genetic Genealogy
Subscribe to get the latest posts sent to your email.
Dear Roberta,
Thanks for your video and article on the x-chromosome.
A question about ‘identical by chance’. The rule of thumb seems to be that if a shared autosomal segment is 15cM long, it is almost certainly ‘identical by descent’, and there is increasing likelihood of ‘identical by chance’ as segments grow smaller. Do the same probabilities apply to segments of x-chromosome? Or does an x-chromosome segment have to be longer than 15cM to be certainly ‘identical by descent’?
Best wishes to you.
Scott Swanson
sswanson@butler.edu
Rule of thumb for the X is that it needs to be twice as large. So 15 cM is the same as 7.5 cm on the other autosomes. That’s because the X has about half as many SNPs. I’m pretty sure I talked about that in the article but didn’t have time in the video.
So smaller segment matches are less reliable.
At least FTDNA doesn’t use any stupid algorithms like Ancestry’s Timber — if there is any 15 cM rule, Timber freely ignores it, sometimes “adjusting” sharing by far more than that. Timber reduced my daughter’s sharing with a 2nd cousin once removed by 40 cm, from 87 cM to 47 cm — and this for someone who is MY 2nd cousin, with whom I have sharing of 264 cM!
Personally, I don’t think double 15 cM should be the test of whether a segment on the X chromosome is Identical by Descent or by Chance. That’s a long segment to be merely “randomly aligned”, especially for males. We don’t even have a second X chromosome to complicate things.
The real question is more one of whether it’s by recent descent or more distant descent, and for a 15 cM segment either is possible. The single segment I share with my own grandmother is only 20 cM; the rest of my entire X chromosome is from my maternal grandfather’s mother. My oldest brother’s entire X chromosome is from her, as well.
This was a nice presentation. I’ve managed to make good use of X-DNA, in particular to identify the (NPE) father of a cross-Atlantic match who I shared more than half my X chromosome with, despite being something like 4th cousin once removed. From her family tree, she should not have any ancestors from my country, and it’s safe to say I’d never worked it out without limiting it to my X-line cousins.
I’ve also run into some traps. Before I tested my parents, I had an X match, I looked at her tree and although I couldn’t find a common ancestor, she was from the valley where my maternal line comes from. So that’s settled, right? Imagine my surprise when my mom’s test came through and this woman was NOT a match!
From what I’ve worked out, it seems that although I inherited an X segment from my mom in common with this woman, the small autosomal regions I share with her actually come from my dad. Because FTDNA filters out X matches which aren’t autosomal matches, she doesn’t show up for my mom.
I think we should work out a standard way to talk about X-relatedness. I’ve used “X-cousins” here, and that works, but I’d wish there was some standard way to say “n-step X line relative” which could instantly tell you your likelihood of being an X match and the expected X DNA shared.
23andMe is the only company that uses the X for matching per se. That is, they will report a match even if the X is the only segment involved. FTDNA will include information about an X segment if a person is first matched with an autosomal segment.
They stopped reporting that. I can’t check now either without the chromosome browser. I don’t have a test on the current chip and I’m not going to retest.
They have resumed reporting it. I think this is probably limited to premium members, though.
You’re correct that you do need a test on the current chip. 23andMe very recently restored the chromosome browser.
I saw that but only on the current chip AND with a subscription. They took it away from all of us and only returned it selectively.
I’m furious.
Actually, even though I meet both conditions — current chip, subscription — I don’t like it either. I think it’s much more valuable to me to have as many of their customers fully engaged as possible. The more “conditions” put on them, the less likely that is to happen.
I didn’t delete my data before but I’m sure tempted to now. I’ve already tested twice, on two chips, and I’m not about to test a third time to get truncated, limited results.
Yes, I understand why some are angry enough to delete their data — which is exactly what I’m talking about. I’ve made the decision to “go along”, but that doesn’t mean everyone will. And when they don’t, of course, that doesn’t just affect 23andMe — but folks like me, as well. Not that I blame you.
You’re absolutely right.
Roberta: Watching the “X” presentation I need to expand my earlier response. My wife’s parents are full 1st Cousins through their fathers. My children are their own third cousins, LoL.
Regards, John Davidson
Dear Roberta:
A bell-shape curve question this time.
On FTDNA I have 5971 autosomal matches and 4 x-chromosome matches, three of whom are siblings My brother has 6204 autosomal matches and 8 x-chromosome matches, three of whom are siblings. Our two sisters, of course, have many more.
Are our x-chromosome matches at the low end of the bell-shaped curve, not least because our mother’s family, compared to our father’s immigrant family, accounts for by far the greater number of matches on FTDNA?
Thanks again.
Scott Swanson