View Full Version : Are there X chromosome haplogroups? How do I find out my X chromosome?

09-18-2017, 02:38 AM
Hi everyone, I am Peter Redmayne. :) I have taken both 23andme and FTDNA. Is there a certain way to find out what kind of X chromosome you have? (Even if you've taken these tests.)

Also, what websites would I need to go to - to find information on mutations/Haplogroups for the X chromsome? (X-DNA?)

Thank you all for the feedback. (I'm new here and sorry, I forgot to make an introduction thread.)

01-16-2018, 05:08 AM
In many ways, the X chromosome is more like the autosomes than it is like the Y chromosome. What do I mean by that? Simply that while the Y chromosome essentially does not change except through mutation, the autosomes and the X chromosome are constantly altered through recombination.

The only exception is when an X chromosome is passed from a father to his daughter. In that case, the X chromosome cannot really recombine -- except in a very small region at each end of the chromosome called PAR1 and PAR2 (for "pseudoautosomal recombining region").

At 23andMe, these two regions are not even included with the Y chromosome. They're included with the X chromosome, since 23andMe has no way of knowing which of each SNP pair belongs to the X, and which to the Y. (Same as they can't tell which SNP in each pair on the autosomes belongs to which copy.)

My brothers and I have Y chromosomes that are virtually identical to that of our father, just as his is essentially identical to that of his own brothers and his father, and so on. For that matter, my Y chromosome will have very few changes from the Y chromosome of my 5th great grandfather on my surname line, who is the man who brought our surname to America. (Of course, in its pre-Americanized form.)

The same thing can't be said for my X chromosome. Although it was passed on to me by my mother, it isn't identical to either her paternal or her maternal copy. It's much more like her paternal copy -- only 20 cM surrounding the centromere came from my mother's mother -- but it does contain DNA from both grandparents. This is also true for the X chromosome of my 2nd brother, and my 2nd and 3rd sisters. We four inherited different copies of our maternal X chromosome.

By chance, two siblings -- my 1st brother and 1st sister -- happened to inherit an X chromosome which contains DNA from our grandfather only. So the X chromosome can be passed on "intact" from a single maternal grandparent, but more often it will recombine.

Of course, all three of my sisters inherited an identical copy of their paternal X chromosome, but most likely it contains DNA from both of our father's maternal grandparents. So again, the X chromosome isn't really stable enough to talk about haplogroups -- at least, not in the sense of the Y chromosome or mtDNA.