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Thread: Ancestry Composition X Chromosome inconsistency between father and daughters

  1. #1
    Registered Users
    Pittsburgh, PA, USA
    (U.S.) American
    Y-DNA (P)
    mtDNA (M)

    United Kingdom Germany Bayern Catalonia France Ireland Switzerland

    Ancestry Composition X Chromosome inconsistency between father and daughters

    Okay, here's a question:

    Why would Ancestry Composition show inconsistent results between a father and his daughters on the X chromosome?

    To be clear, the results aren't totally inconsistent. That is, my father and all three of his daughters show "Southern European" on the X chromosome, in the same region. This encompasses roughly the first three-fourths of the chromosome. The remainder shows up as "broadly Northwestern European", but nothing more specific.

    However, drilling down a bit deeper, the bulk of the Southern European portion of my father's X chromosome shows as "Italian" -- probably about two-thirds of it, or around half of the chromosome. This segment accounts for all of my father's 1.3% Italian.

    Meanwhile, none of my sisters shows any Italian on the X chromosome. My youngest sister, in fact, shows nothing more specific than "broadly Southern European" (in addition, of course, to the "broadly Northwestern European" part). The other two sisters also show a little bit of Balkan -- 0.4% for one (in the form of a single segment), and 0.3% for the other (in the form of two segments in approximately that same location as the other sister's one segment).

    The excuse that each of my sisters has two X chromosomes seems pretty lame to me, since they're being phased against their father. All 23andMe has to do is ensure that one of each of my sister's two X chromosomes matches our father's exactly. The only place this could be a problem would be at the very ends, but the inconsistency isn't limited to just the ends.

    Can anybody account for this?
    Last edited by geebee; 08-03-2016 at 06:33 PM.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.


  2. The Following User Says Thank You to geebee For This Useful Post:

     palamede (08-29-2016)

  3. #2
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    Y-DNA (P)
    mtDNA (M)

    United States of America Canada
    I think it is a bit of a stretch to try and get any ancestry composition information from the X-chromosome. I would put my efforts elsewhere.

    PM me if you wish to discuss further.

    Jack Wyatt

  4. #3
    Registered Users

    Your sisters, of course, have an identical X chromosome to your father, by definition. I think there's not much you can say here other than 23AndMe is inconsistent, which has been established elsewhere too, but it's good to get definitive examples like this.

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