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I'm sure I am being thick

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  • I'm sure I am being thick

    Hi

    The attached section of the chromosome browser compares me with a first cousin on my dad's side (blue), and a first cousin once removed on my mum's side (orange).

    There are several sections of overlapping segments which I have always assumed means the three of us share a common ancestor, which is of course possible, bu I have no idea where or when.

    First question - Is my assumption of a common ancestor for us all the correct one?

    Second question - If so, why doesn't mum's cousin (orange) show up in my cousin's (blue) matches?

    Thanks all

    Mick
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  • #2
    We have two of each chromosome, a maternal(50% of DNA inherited of mother) and a paternal (50% of DNA inherited from father).
    23 pairs of chromosomes, 46 Single Chromosomes
    Roughly 3400cM on our maternal chromosomes and another 3400cM on our paternal chromosomes, A total of roughly 6800cM in total DNA

    Chromosome browser merges the two into one because they can not tell you which is which due to nature of test.

    Blue match in this instance will most likely be a matching segment on your paternal chromosome and the orange a matching segment on your Maternal chromosome.
    Last edited by prairielad; 22 September 2017, 07:29 PM.

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    • #3
      Thanks

      That's terrific, Prairielad.

      Thanks for explaining.

      Best

      Mick

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      • #4
        Originally posted by prairielad View Post
        We have two of each chromosome, a maternal(50% of DNA inherited of mother) and a paternal (50% of DNA inherited from father).
        Just want to double-check I have this right - for each of us, one of each pair is from our mother, one of each pair is from our father --

        But when creating sperm and egg - each of which only contains one chromosome of each pair - that chromosome is a mishmash of parts from each of the pair - as opposed to being either the chromosome from your mother or the chromosome from your father.

        --Both statements correct, or ??

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        • #5
          You have one chromosome in each pair from your mother. That chromosome is usually made up of segments from the chromosome she got from her mother and of the chromosome she got from her father. Segments are swapped in a process called recombination. Occasionally recombination doesn't occur, and you get one of your grandparent's entire chromosomes.

          The other chromosome in the pair comes from your father, and likewise is usually made up of segments from both of his parents.

          The DNA test can't tell which chromosome came from which parent.

          But the chromosomes you receive from each parent stay separate (do not recombine) in your cells. They only recombine in the egg or sperm cells (depending on your sex) you produce.

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          • #6
            You might want to read The Family Tree Guide to DNA Testing and Genetic Genealogy by Blaine T. Bettinger. It's available at Amazon. Your local library might have a copy.

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            • #7
              Thanks

              That's really useful, MoberleyDrake. Thanks so much.

              Actually I have the book you mention on my ipad but had forgotten and it is unread. I shall remedy that immediately.

              Thanks again.

              Mick

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