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Can someone set me straight?

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  • Can someone set me straight?

    Hi all,

    So I've noticed some things about the X chromosome that I don't quite understand...

    FYI, I am female and have had both my parents' DNA tested also. It's very easy to know which DNA match, matches which side of the family, especially because my Mum is Maltese/Italian.
    I have a DNA match who my Dad and I share, I share about 45 cm and my Dad 46 cm with this woman. But she also matches me on my X chromosome, but not my Dad's. I don't understand why she would match me on the X and not my Dad? What is the threshold for a significant match on the X?
    Because we have common X DNA, I have assumed she matches me somewhere on my Dad's mother's side...am I safe in that assumption?

    Also on Gedmatch, I have noticed that I have a lot of X chromosome matches, but many share no autosomal DNA. What is the significance of this? Is it because the X goes through less recombination than the other chromosomes?

    Thanks for your help!

  • #2
    While I may not be answering your Q's, There is a thread on the X at this site that maybe of some interest to you. https://www.facebook.com/groups/dnanewbie/ it also has a link to http://www.thegeneticgenealogist.com...-x-chromosome/

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    • #3
      Originally posted by sarahmj View Post
      Hi all,

      So I've noticed some things about the X chromosome that I don't quite understand...

      FYI, I am female and have had both my parents' DNA tested also. It's very easy to know which DNA match, matches which side of the family, especially because my Mum is Maltese/Italian.
      I have a DNA match who my Dad and I share, I share about 45 cm and my Dad 46 cm with this woman. But she also matches me on my X chromosome, but not my Dad's. I don't understand why she would match me on the X and not my Dad? What is the threshold for a significant match on the X?
      Because we have common X DNA, I have assumed she matches me somewhere on my Dad's mother's side...am I safe in that assumption?

      Also on Gedmatch, I have noticed that I have a lot of X chromosome matches, but many share no autosomal DNA. What is the significance of this? Is it because the X goes through less recombination than the other chromosomes?

      Thanks for your help!
      What size is this X match?
      You have 2 X's, while your father only has one. If this X match is small, it could be a false segment due to algorithm picking values from both your X's to create a IBS segment.

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