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Cousin conundrum

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  • Cousin conundrum

    Can anyone help with this one-I am writing on behalf of my mother and her results:

    She is half UK half unknown American.

    She has 3 cousins who all match in the same location:
    Cousin A who is half UK half German.
    Cousin B who is German.
    Cousin C who is British.

    Cousin A matches B and C BUT B and C don't match each other.

    So...I'm thinking Cousin B matches Cousin A on his German side.
    Cousin C matches Cousin A on his British side.

    What about my mother? She matches ALL of them!! So by sheer flook, is she related to B and C via each of her parents and also obviously cousin A, it's just that due to not being able to test her parents, we will never know whether we are connected to cousin A via his UK side or his German side?!

    I hope that makes sense

  • #2
    Your explanation could be the case, or it might be that your mother and A are both identically heterozygous at some location on the segment whereas B and C are each differently homozygous at the same location but with one base that matches either your mother or A. That would allow your mother and A to match B and C but preclude B and C from matching one another.

    One way to discern whether that is the case is to dial-down the cM for all these matches and see if B and C match on fractions of the segment.
    Last edited by tomcat; 4 November 2012, 08:10 AM.


    • #3
      I was just wondering what happens if you compare them all on the Chromosome Browser set at 1+cM is there any overlap?
      Last edited by EdwardRHill; 4 November 2012, 11:27 AM.


      • #4
        Thanks for the replies. I have a confession to make-the results are at
        23andme so I can't see any smaller matches I hope it's ok to ask about them here, Mum has done FF too but these cousins haven't.
        The thing that is bugging me is that cousin B has connections to a region of Romania that some of my mother's different cousins do.

        Tomcat, what does it mean to be identically heterozygous in terms of ancestry? Is that like UK/Ger whereas homozygous would be UK/UK or Ger/Ger?!
        Last edited by Boudicca; 5 November 2012, 03:19 AM.