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X matches that show as Zero in FF

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  • X matches that show as Zero in FF

    Just an FYI

    FTDNA only reports an X match if the X segment is 10.00 or greater. Otherwise, you see 'No Match' in the Detail View or 0 in the Table View.

    But you may have X matches between 6 and 10.

    My mother has a segment of 9.99 cM of X, which does not show except via the Chromosome Browser. She also has 26 cM of X with one match, spread out over three segments of 9.5, 9.5 and 7.0. But she sees No Match or Zero in the main views.

    My mother shows 66 official X matches, for segments over 10. But she has about 1050 X matches if you include all the matches from 6 to 9.99

    I am not saying X matches from 6 to 9.99 are particularly useful. They are likely very distant or false.

    But I still think its misleading to call them Zero or No Match.


    Males have far fewer X matches and I dont see X matches from 6 to 10 on my account. OTOH, I have only 8 X matches total.

  • #2
    The observation that males have "far fewer X matches" has troubled me for a long time. The same situation, although possibly with a completely different matching algorithm, caught my attention years ago on GEDmatch, where I found that females tended to have at least 10 times more X matches than males (I don't remember the exact figure, it may have been much higher!). That doesn't sound logical, and it made me suspect that most of the X matches for females, particularly the smaller segments, could well be false, the result of the algorithm "switching back and forth" between paternal and maternal copies of the X chromosome. Until we can obtain accurate "phased" X chromosome data or real sequence data from "long-read sequencing", we will never know how accurate the segment matching algorithms are.