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cm's shared on X. Grandmother or Great Aunt?

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  • cm's shared on X. Grandmother or Great Aunt?

    How many cm's should/can a grandmother match you on the X? Is 52.02 cm on the X in line with grandmother or more in line with great aunt? I'm new to DNA. Thank you.

  • #2

    I share 17cm with my Grandmother, the rest came from my Grandfather.

    as a male I share 100% with my Mother.

    Since my Grandfather got his X from his mother I actually share much more with my Great Grandmother than my Maternal Grandmother.


    • #3
      This is very interesting. Thank you for your reply, jova99.

      It seems I may never find the answer to my question as I am not well versed in genetics and there is so much variation. I think my great aunt may be my grandmother but I may never know.


      • #4
        You can share anything from 0 to 100 percent of X with a Grandparent

        A female will always share 100% with paternal Grandmother as her father only had one X which was passed onto her intact which he received from his mother (females paternal Grandmother)
        A female will also match 0 to 100% to her maternal Grandmother and or maternal Grandfather, depending on how much recombination happened between her mothers maternal and paternal X when it was passed on to her.
        Recombination of chromosome pairs does not always happen, sometimes full maternal or paternal chromosome is passed on to child.

        A male is like the second scenerio above, 0 to 100% of his maternal Grandmother and or maternal GRandfather.

        I am not sure what the average is for matching a Grandparent on X is.
        X segment sizes are rarely used in determining relationship level based on cM due to its unique inheritance pattern, no male to male transmission and no recombination every father to daughter transmission (as well as the normal non recombination which happens at times in daughter to daughter transmission)
        Last edited by prairielad; 14 June 2017, 09:15 PM.


        • #5
          Many thanks, Prairielad, for the most excellent explanation of X inheritance. It seems this route is not the best one for determining relationship but at least I have much greater understanding of the X. Thanks again.