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Difference in number of X-DNA matches between brother and I

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  • Difference in number of X-DNA matches between brother and I

    I’ve noticed something interesting today on my Family Finder. My brother has approximately 125 matches on his X chromosome out of 30 000 FF matches (which is less than 1 % of his total matches). While I’ve got 437 matches out of 27 000 FF matches (which is approximately 1,6 % of my total matches). The difference in number of X-DNA matches between my brother and I surprises me since we’re both males (meaning that we only inherited one X chromosome from our mother). That said, we’re 3/4 Ashkenazi (from our father and maternal grandfather) and 1/4 Sephardic (from our maternal grandmother). So I wonder if this means that I inherited my maternal grandfather’s X chromosome while my brother may have inherited more of a mixture of my maternal grandparent’s X chromosomes. That said, how many X-DNA matches do fully Ashkenazi women (who did not test their parents) tend to get on Family Finder? Any insight(s) on the matter will be gladly welcome here.

  • #2
    Of course, the X chromosomes which you and your brother received from your mother are different, so I wouldn't be too worried in the difference in matches between you and your brother,

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    • #3
      Originally posted by georgian1950 View Post
      Of course, the X chromosomes which you and your brother received from your mother are different, so I wouldn't be too worried in the difference in matches between you and your brother,
      Thanks for your answer. How many X-matches do you (or your siblings) have? Are you Ashkenazi?
      Last edited by Power77; 13 September 2022, 03:24 PM.

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      • #4
        Originally posted by Power77 View Post

        Thanks for your answer. How many X-matches do you (or your siblings) have? Are you Ashkenazi?
        I am not Ashkenazi. I only have 2 X-matches on FF, one of which is my mother. My mother has 38, one with me. My 17% Ashkenazi step daughter has 174 matches.

        I would not worry too much about X-matches which are more than a few generations back. I am doing some research on distant X-matches which I hope will shed a new light on the subject. Hope to have something out soon.

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        • #5
          Originally posted by georgian1950 View Post

          I am not Ashkenazi. I only have 2 X-matches on FF, one of which is my mother. My mother has 38, one with me. My 17% Ashkenazi step daughter has 174 matches.

          I would not worry too much about X-matches which are more than a few generations back. I am doing some research on distant X-matches which I hope will shed a new light on the subject. Hope to have something out soon.
          Interesting, I thought women would have had a MUCH higher number and percentage of X-matches than that. Does your mother’s and stepdaughter’s X-DNA raw data look different from yours in terms of heterozygous calls (such as AG, CT, or AT)?

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          • #6
            I really haven't looked at that. I need to put together my blog on X-matching, because if I present it piecemeal, people will say "you are crazy". Basically the threashold for X-matching should be a whole lot lower. FTDNA sets its parameters at a very high level.

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