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  • FF Query

    My son and I have a FF match.We both match someone on ChrY 4 and 6. My son's ChrY 4 14.6 cM 2791, 2.92 cM 600 ChrY 6
    1.09 cM 2300. Mine, ChrY 4 9.69 cM 2094,4.5cM 597, ChrY 6 1.93 cM 4700. Why has my son more SNPs matching on ChrY 4 than me? Why are there more SNPs matching at 1.93 cMs than 9.69 cMs.

  • #2
    ChrY is a typo, isn't it?

    Originally posted by 1798 View Post
    Why has my son more SNPs matching on ChrY 4 than me?
    Your son got 40-60% of his autosomal DNA from his mother. So it is most likely a compound segment.

    Originally posted by 1798 View Post
    Why are there more SNPs matching at 1.93 cMs than 9.69 cMs.
    Because centiMorgans do not measure SNPs, they are a measure of recombination frequency (or something similar equally complicated...).

    See the Family Tree DNA Learning Center for additional details:

    Comment


    • #3
      Originally posted by dna View Post
      Your son got 40-60% of his autosomal DNA from his mother. So it is most likely a compound segment.

      Because centiMorgans do not measure SNPs, they are a measure of recombination frequency (or something similar equally complicated...).

      See the Family Tree DNA Learning Center for additional details:
      I was too lazy to write chromosome.
      How could my son and I have a cousin match that involves his mother's dna? I don't have the same dna as my wife.

      Comment


      • #4
        Originally posted by 1798 View Post
        I was too lazy to write chromosome.
        There is no Y in chromosome...

        Originally posted by 1798 View Post
        I don't have the same dna as my wife.
        Actually yes, you do. We all share most of the DNA, just some SNPs are different. But that is irrelevant in this discussion.

        Originally posted by 1798 View Post
        How could my son and I have a cousin match that involves his mother's dna?
        Look up the results in the Family Finder Table View. Write down Start Location and End Location for the matches you and your son have with the cousin. Get CSV files for yourself and your son. Load them side by side into a spreadsheet. Verify how many SNPs were needed to be coming from his mother DNA, so he would match the cousin in a longer stretch than you do.

        Comment


        • #5
          I have attached a portion of my phased results regarding how my father and I match his paternal 1st cousin.
          According to FTDNA's Start/Stop points, I share a larger overlapping segment then my father with his paternal 1st Cousin.
          My father to his 1st Cousin 9.82cM, 1473 SNPs
          Myself to same 1st Cousin 12.09cM, 1873 SNPs

          Looking at our phased results it shows why my segment is shown to be longer (in regards to the end of segment). Algorithm is picking values from my fathers paternal 1st cousins maternal and paternal chromosomes and matching it with my maternal chromosome. It is not that he is sharing recent ancestor with my mother, it is just creating a false(IBS segment)matching segment because algorithm does not know which is the maternal value vs the paternal value and is looking for lengths of unbroken DNA between two people.

          This will happen at either end of matching segment.

          Blue represents the possible combinations Algorithm would find as a possible unbroken segment.
          Red show where my father stops matching his Paternal 1st cousin (his value for position 123865783 is TT)
          Brown shows where I stop matching his Paternal 1st cousin

          edit
          Column listed as Father in my Father's 1st Cousins results refer to his father (his paternal chromosome), Mother refers to his maternal Chromsome.
          Attached Files
          Last edited by prairielad; 13 October 2014, 09:13 PM.

          Comment


          • #6
            Originally posted by prairielad View Post
            I have attached a portion of my phased results regarding how my father and I match his paternal 1st cousin.
            According to FTDNA's Start/Stop points, I share a larger overlapping segment then my father with his paternal 1st Cousin.
            My father to his 1st Cousin 9.82cM, 1473 SNPs
            Myself to same 1st Cousin 12.09cM, 1873 SNPs

            Looking at our phased results it shows why my segment is shown to be longer (in regards to the end of segment). Algorithm is picking values from my fathers paternal 1st cousins maternal and paternal chromosomes and matching it with my maternal chromosome. It is not that he is sharing recent ancestor with my mother, it is just creating a false(IBS segment)matching segment because algorithm does not know which is the maternal value vs the paternal value and is looking for lengths of unbroken DNA between two people.

            This will happen at either end of matching segment.

            Blue represents the possible combinations Algorithm would find as a possible unbroken segment.
            Red show where my father stops matching his Paternal 1st cousin (his value for position 123865783 is TT)
            Brown shows where I stop matching his Paternal 1st cousin

            edit
            Column listed as Father in my Father's 1st Cousins results refer to his father (his paternal chromosome), Mother refers to his maternal Chromsome.
            Thanks. I was trying to determine if the match my son and I have is on my side of the family. I would know better if I could get my wife to take the FF test.

            Comment

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