No autosomal match to YDNA or mtDNA
Why oh why doesn’t that YDNA match show up in the list of autosomal matches?
And why isn’t that perfect mitochondrial DNA (mtDNA) match sitting next to me in the autosomal testing pool?
The Legal Genealogist can’t resist a pun, so … why is the chair empty in both of these cases?1
That’s a question that turns up a lot in email especially as DNA sales bring more people into the testing pool, and especially when people are taking a variety of DNA tests the way they can at Family Tree DNA.
Person A takes a YDNA test and is a perfect 67-for-67 marker match with Person B. But Person B isn’t on the match list for cousins in Person A’s autosomal DNA test results.
Or Person C takes an mtDNA test and is a perfect match — a genetic distance of 0 — from person D. But Person D isn’t on Person C’s autosomal match list either.
When the testing company says, as Family Tree DNA does, that the common ancestor for that that 67-for-67 marker YDNA match is predicted to be found, “50% of the time, in three generations or less and with a 90% probability within five generations”2 or that the mtDNA match can be found, 50% of the time, within five generations3 — but they’re not in the autosomal matches, where we expect to find our cousins “within the last five generations”4 — it’s easy to see why people get confused.
There are two basic reasons why that YDNA match or mtDNA match isn’t on an autosomal match list at Family Tree DNA, the only company that offers all three types of testing:
1. The person you’re looking at has taken the YDNA or mtDNA test — but hasn’t done autosomal testing.
Person B is never going to show up on Person A’s autosomal match list if Person B hasn’t taken the autosomal test. Same for Person D: not going to be in Person C’s autosomal matches without doing autosomal testing. And a fair number of people do one, and only one, kind of DNA test.
In my uncle’s YDNA match list, for example, only one of his 67-for-67 marker matches has done autosomal DNA testing; the other two have done YDNA tests only.
How can you tell?
It’s easy: in your match list for either YDNA testing or mtDNA testing, you can see whether the person you match has taken the autosomal test — called Family Finder at Family Tree DNA.
For YDNA, under the name of each match, you’ll see a set of icons and letters that look something like this:
The first icon is for email — you can click on that to contact the match directly. The second is TiP — a calculator to help us understand how likely it is that the match shares a common ancestor within a genealogical time frame. The third is for a notes field, where you can add any comment to yourself you’d like to note about this match. The fourth tells you the person has uploaded at least a minimal family tree.
The fifth tells you exactly which YDNA test the person has taken — in this case a 67-marker test. If the match had tested to 111 markers, it would say Y-DNA111. And then come those all important letters for autosomal testing: FF. If those are there, the person has done the Family Finder autosomal test. If they’re not, then he hasn’t taken that test — and he won’t ever be on an autosomal match list.
For mtDNA, the icons are to the right of the match’s name and look something like this:
Again, the first icon is for email. The second is for notes. The third tells you there’s a family tree associated with the match.
The fourth here tells you which mtDNA test the person has taken — in this case, FMS for full mitochondrial sequence. (It’d say HVR1 or HVR2 if the person had taken a more limited mtDNA test.) And the last one — that FF again — tells you this person did take the autosomal test. If those letters aren’t there, the mtDNA match won’t ever be on the autosomal match list.
2. You don’t share enough autosomal DNA with the person you’re looking at to show up.
If those critical FF letters are there, and the person still isn’t on the match list, it simply means that you and your match don’t share enough autosomal DNA to show up as a match. That usually means the common ancestor is just too far back in time for you both to have inherited big enough chunks of autosomal DNA from that ancestor.
What’s important to understand here is this: YDNA and mtDNA are fairly stable from generation to generation. In most cases, there aren’t huge changes in the DNA markers as they get passed down from father to son to son in YDNA or through the direct maternal line for mtDNA. So it’s not uncommon to see these kinds of DNA passing unchanged through many generations.5
Yes, the overall odds may be 90% that two men who share a surname who match at 67-for-67 markers in a YDNA test have a common ancestor within five generations. But that’s pure chance: that common ancestor could be many generations back. And because mtDNA is even more stable than YDNA, the chance is excellent that the common ancestors for two people who’ve tested their mtDNA will be many generations back, often back before genealogical records started being kept.
Autosomal DNA is different: you get this kind of DNA from both of your parents, not just the paternal or maternal side, and it doesn’t stay the same from generation to generation. Instead, each individual gets a random mix from the parents in a process called recombination.6 And because of recombination, you and a cousin just might not get enough of the same kind of DNA from an ancestor to show up on each other’s match list.
The odds are that one in 10 sets of third cousins may simply not inherit enough autosomal DNA in common with each other to show up on each other’s autosomal match list. About half of fourth cousins won’t inherit enough in common. And only one in 10 sets of fifth cousins will get enough to show up on an autosomal match list.7
So… look at each set of results independently. You can have a perfect YDNA match or mtDNA match from a common ancestor who lived many many generations ago, so that match won’t be on your autosomal match list at all. Or you just may need to nudge that cousin to take an autosomal test he or she hasn’t taken yet.
- Why empty… Y mt… You get it, right? ↩
- “If two men share a surname, how should the genetic distance at 67 Y-chromosome STR markers be interpreted?,” Learning Center, Family Tree DNA (https://www.familytreedna.com/learn/ : accessed 2 Dec 2017). ↩
- Ibid., “Maternal Lineage Tests.” ↩
“Autosomal Tests (Family Finder).” ↩
- See generally “Introduction to Molecular Genealogy,” Genetic Science Learning Center, University of Utah (http://learn.genetics.utah.edu/ : accessed 2 Dec 2017). ↩
- See ISOGG Wiki (http://www.isogg.org/wiki), “Recombination,” rev. 2 Dec 2017. ↩
- “What is the probability that my relative and I share enough DNA for Family Finder to detect?,” Learning Center, Family Tree DNA (https://www.familytreedna.com/learn/ : accessed 2 Dec 2017). ↩