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Matching on the X Chromosome

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  • Matching on the X Chromosome

    I was just checking GEDMATCH and noticed I now have an X chromosome match that is nearly perfect...

    Chr Start Location End Location Centimorgans (cM) SNPs
    X 2,625,987 154,662,855 191.0

    Total Autosomal DNA match is just over five Cm even if I reduce the matching size to 1 cM though so it has to be a fairly distant match in terms of generations.

    What does this mean? The more I think about it the more confused I become. Clearly there is some part of this whole DNA thing that I'm not understanding.

    I'm starting to think there may be a GEDMATCH bug.
    Last edited by 1_mke; 3 March 2012, 09:49 PM.

  • #2
    First, to be sure you are not picking up noise, change your defaults to 5cm min and 500 SNPs and see if you still match and I'll answer your original question.

    Matt
    Last edited by mkdexter; 3 March 2012, 09:56 PM.

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    • #3
      Matt,
      Same result if you meant to do this on the X chromosome...

      Largest segment = 191.0 cM
      Total of segments > 5 cM = 191.0 cM Actual.

      I can PM you the kit numbers if you are interested in taking a look.

      Comment


      • #4
        I think I've figured it out. Looks like a bad upload. All the matches are No Calls. My raw file has been there for awhile so it must be the other one that is messed up. Apologies for the false alarm.

        In general though this scenario should be impossible I think?

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        • #5
          I'll look if you want .cant for an hour though. Gotta drive across town... Yes as you say the results can be questionable. 196cm is the full match size. 196 cm would be a child, parent, sibling, grandparent, great grandparent, or close cousin and only in certain cases....since X is not passed from father to son. Matt
          Last edited by mkdexter; 3 March 2012, 10:19 PM.

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          • #6
            Here's the record I was talking about, though I'm not appearing on this list.

            http://ww2.gedmatch.com:8007/autosom...7&x_cm_limit=3

            My GedMatch ID is M204225

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            • #7
              That one is definitely not matching.

              http://forums.familytreedna.com/atta...1&d=1330873572

              Following I have three examples to show you what a good match will look like.
              Attached Files
              Last edited by mkdexter; 4 March 2012, 09:10 AM.

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              • #8
                My X 23andM3 to my X FTDNA
                http://forums.familytreedna.com/atta...1&d=1330873666
                Attached Files

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                • #9
                  FTDNA myself to my daughter, X

                  http://forums.familytreedna.com/atta...1&d=1330873731
                  Attached Files

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                  • #10
                    X, daughter to maternal grandmother FF test.

                    http://forums.familytreedna.com/atta...1&d=1330873937
                    Attached Files

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                    • #11
                      Agreed. There is something very odd about that record and I was confused by the table at the bottom. The color of the graphic and the fact that it is associated with no calls should have jumped out at me more quickly. Something appears to be broken.

                      Thank you Matt.

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                      • #12
                        Originally posted by mkdexter View Post
                        X, daughter to maternal grandmother FF test.

                        http://forums.familytreedna.com/atta...1&d=1330873937
                        Yup, mine look the same grandmother > son > daughter. From the matches however it appears the grandmother's X is a mix of her two parents'.

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