geebee
08-03-2016, 06:30 PM
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?
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?