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Thread: Ancestry Composition X Chromosome inconsistency between father and daughters

  1. #1
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    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 07:33 PM.
    The short explanation of my ancestry is British-German-Catalan, but it actually includes smaller amounts of French, Irish, Swiss, Choctaw and probably Cherokee. My avatar picture is of my father, his father, and his father's father. The baby in the picture is my eldest brother.

    GB

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

     palamede (08-29-2016)

  3. #2
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    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
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    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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