Why isn't X DNA used in genealogy?

+10 votes
I wonder why only Y, mtDNA and auDNA are used in genealogical genetics, why isn't X DNA used as well?
in WikiTree Tech by Living Farrar G2G6 Mach 1 (16.3k points)
retagged by Peter Roberts

3 Answers

+8 votes
X DNA is used, but it's part of the auDNA package.  But it does have a different inheritance.  than the other chromosomes and so it's kept separate.  Men have one X and one Y while women have 2 Xs.  Men can pass their X to a daughter, but not to a son.  Women will pass one of their 2 Xs to a son but daughters get one from their mother and one from their father.  Sons always have their father's Y.  At any rate, on GEDmatch you can compare Ys (at least from Ancestry.comDNA.  I'm not sure about the other Genealogical Testers.
by Living Dardinger G2G6 Pilot (449k points)
You forgot to mention that the  XDNA passed on by Mom is recombined from ther two X's

As I understand it XDNA tracks differently than mtDNA, and can be used to eliminate spurious matches.  If I recall correctly 23andme does have X DNA matching, as well as auDNA matching. In other words XDNA matching is more narrow than auDNA, just as YDNA is more narrow than auDNA.

As a male I have recombined X DNA from my mother, as well as au
DNA from Mom and YDNA from Dad as well as auDNA from Dad.

Mom got her Dos Equis from  Mom and Dad, Dad got  a recombined X from Mom and a Y DNA from Dad.

Mom's recombined XDNA contains her Dad's unrecombined XDNA and her mothers recombined XDNA.

It seems to me that tracing this X DNA, as opposed to auDNA, would provide a more narrowly defined, and thus more accurate, match.

Alas, Family Finder does not provide X as well as auDNA.
Family Finder provides X-DNA matching. It is hidden under the drop down menu labeled "Relations: Show All Matches".
Thanks Pete
+5 votes
by Peter Roberts G2G6 Pilot (726k points)
+4 votes
23andMe does incorporate X segments into its matching algorithm. AncestryDNA and FTDNA do not, but FTDNA will display X segments of all sizes for people who qualify as matches with an autosomal segment. It's best to ignore the smaller segments at FTDNA, especially for female-female comparisons.
by Ann Turner G2G6 Mach 1 (17.6k points)

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