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  • #16
    Originally posted by S9 H9 View Post

    In my One-to-Many matching at gedmatch.com, only 4 of my matches in the X-DNA column is with males, while I have nearly 30 with females. This is on a very long list of 669 autosomal matches.
    Just did a long count instead of eyeballing. Turns out I have 74 X chromosome "matches" with females, but only 4 with males. That is a ratio of 18.5 times more female "matches" than male matching on my X chromosome.

    This is the problem with unphased SNP comparisons.

    And of those 74 female matches, the only one I'm going to invest my time in, as in a "real" match, is the one whose father is also tested and whom I also match on the exact same spot on his X chromosome.

    Out of that 74 female X matches, the longest segment is a mere 5.5 cM.

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    • #17
      I have 890 matches at Gedmatch (threshold set at 7cMs) and 515 of these are also X chromo matches. I am particularly interested in one of my female matches who shares 41.8 cMs longest segment, and 66.3 cMs, total segments on the X chromo. These are huge numbers compared to the other X matches. Just curious as to what these large numbers could possibly mean?

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      • #18
        Originally posted by marietta View Post
        I am particularly interested in one of my female matches who shares 41.8 cMs longest segment, and 66.3 cMs, total segments on the X chromo. These are huge numbers compared to the other X matches. Just curious as to what these large numbers could possibly mean?
        Certainly a 66cM match is worth investigating. Even if both of you are matching on the X chromosomes you got from your respective fathers, that big of a segment implies a closer relationship than distant cousin.

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        • #19
          Originally posted by marietta View Post
          I have 890 matches at Gedmatch (threshold set at 7cMs) and 515 of these are also X chromo matches. I am particularly interested in one of my female matches who shares 41.8 cMs longest segment, and 66.3 cMs, total segments on the X chromo. These are huge numbers compared to the other X matches. Just curious as to what these large numbers could possibly mean?
          The segment on the X alone usually means farther than 3rd cousin and the reason is that if two people are closer than 3rd, there is enough DNA shared on all chromosomes, X or not, to indicate they are 2nd, or 1st, etc.

          The 41.8cM segment is your key share. The rest of the 24.5cM would depend on how it sums up; as one second segment or a lot of little segments. If you have a two segment match that is probably coming from the same degree of relationship but if one large and many small segments there is really no way to know where all the smaller ones are from. The good news is the 41.8cM segment. it certainly means there is a valid X chromosome match.

          If it where me, I would presume the 41.8 share, without any other chromosomes matching, has a higher chance of coming from a father to daughter line more than a mother to daughter line. The reason behind that is that more recombination (more chance of losing the large segment) occurs mother to daughter than father to daughter branches. So for a female, this would be her father's side, then her paternal grandparents, for a male, this would be his mother's father's side.

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          • #20
            Matt, as always, many thanks. I do share 3 segments with this match: the X; and chromo 15 with 10.7 cMs; and chromo 3 with 9.8 cMs.
            We designated our g,g,g grandparents as our ancestral couple on the X. The other 2 segment matches we have not yet found. It is just so interesting to get a "trifecta" of X and autosomal matches with the same person. And the large block of cMs on the X was fascinating.

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            • #21
              You probably share all three segments with the same two ancestors (ggggrands).

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