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Chromosome 23

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  • Chromosome 23

    I am male, but recently seen that I matched a female on chromosome 23. Only 2.5 cM. Is this possible? A glitch in a system? If possible, what does it mean. I've never matched anyone on chromosome 23. Thanks

  • #2
    Chromosome 23 is the X chromosome. I don't have any files from FTDNA's new chip, but the kits I manage (all 2017 and earlier) show it as X, not 23.

    Males have one X chromosome, passed down to them by their mother, so it's not a glitch, as a male can match a female or another male on the X. Matches on the X chromosome at FTDNA can be misleading, because FTDNA shows any shared amount on the X as an "X-match," such as your 2.5 cM match. Most advice that I've seen is that a match on the X must be at least double the minimum used for chromosomes 1-22, so 15-20 cM at the least.

    These two pages have good information about the X chromosome for genetic genealogy:
    Roberta Estes also has several good blog posts about the X chromosome. Here are two: