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X matches

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  • X matches

    Can someone tell me what it means when it says X match on one of your matches.

  • #2
    It means you match that person on the X chromosome. Men only have one X chromosome and it comes from their mother.


    • #3
      Beware of putting too much faith in an FTDNA match labeled as an X-match. Most of the time the segment(s) are too small to be considered more than Inheritance By State (IBS, basically by coincidence, false positive), vs. Inheritance By Descent (IBD, actually from a common ancestor). FTDNA will show a match as an X-match even if the segment is tiny. The rule of thumb is that a matching segment on the X chromosome should be at least twice the recommended minimum for the other 22 chromosomes, so instead of a minimum 7-10 cM, on the X you should only consider a minimum segment of about 15-20 cM, preferably larger.

      For further reading about the X chromosome, the ISOGG Wiki page for X-Chromosome Testing has some information, plus links to many site pages with more information. I like the pages shown in the Further Reading section by Jared Smith (X-chromosome recombination), and in the Blog Articles section by Louise Coakley (Geni 1 blog, X-DNA's helpful inheritance patterns).


      • #4
        KATM - What a bonanza of links within links to be explored! I will bookmark all of them. So many of these links I have not seen, so will look forward to a re-education. The "Tips and Warnings About Using X -Dna" I found to be important. Thank you!

        B546846 - In case it is not easily discovered in these links, the X is Chromosome 23.


        • #5
          Most of my x matches are very small. Mostly under 3 cM and only a few above 15 to 20. So mostly IBS

          The easiest way to scan your X matches is to download a .csv file and then sort by Chromosome. Then you can manually scan your X segments for decent size segments.

          By 'Download', I mean DOWNLOAD ALL SEGMENTS found on the upper right of the Chromosome Browser page.

          btw, females have a LOT more X matches than males. But mostly IBS

          I really really wish FTDNA would re-think the X column. Sorting would be nice. And dont make such a big deal of tiny tiny X matches. Print the actual number of cM rather than a super obvious/useless 'X"
          Last edited by mabrams; 11th August 2019, 01:27 AM.