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Female matching father's paternal family

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  • Female matching father's paternal family

    I recently reviewed my "X" matches and found that I (female) match cousins on my father's father's side of the family. Three cousins, one a 1st cousin 1xR, the second is a 3rd cousin and the 3rd match is a 4th cousin (this last one is a cousin from my father's grandmother....while the others are from my father's grandfather). I have no evidence that my father's mother and father were related....in fact, his father was 100% Swiss-German and his mother was 100% Irish and both of these parents were first generation in the US. The segments that I match with are not large....two cousins at about 4.8 cM and the other one is 6.6 cM. I am trying to figure out an explanation. Could it be that my father was a "Klinefelter mosaic syndrome" male? In that case, he would be "XXY" instead of XY. In this case, he could have inherited one X from his mother and an XY from his father. While Klinefelter's syndrome males are infertile, the "mosaic" variant does not usually show any of the symptoms. Is there another more plausible explanation??? Thank You!

  • #2
    Originally posted by spanlin View Post
    Is there another more plausible explanation???
    Yes. I doubt what you're seeing has anything to do with chromosome abnormalities.

    It's very common to have small matching segments that may not be genealogically relevant. And your known genealogical relationship being on your father's side doesn't necessarily mean that these segments are from your father's side -- they could be from your mother's side. It's certainly possible that you could also be very distantly related to these cousins through a totally different line than your known connection.

    Are you able to test either of your parents? Or better yet, do you have any living grandparents who you could test?

    Testing other family members can help determine which line of your ancestry these small matching segments were inherited through.

    Elise
    Last edited by efgen; 26 January 2014, 04:20 PM.

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    • #3
      Are you able to test either of your parents? Or better yet, do you have any living gr

      My parents and my grandparents are all deceased. My brother has been tested and he does not match any of the cousins from my father's paternal line. Of course, I would not expect him to since he gets his "X" from my mother.

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      • #4
        X-DNA could not have been passed through your father's father generation. Any father-son generation kills X inheritance. The X connection with your cousins must be through another path. Even if there was an X connection with close cousins, it would almost certainly be larger segments than the ones you describe.

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        • #5
          Could it be due to Klinefelter's Syndrome (Mosaic Variant)?

          Not sure if this could also be an explanation though....Could my father have had a "Mosaic" variant of Klinefelter's Syndrome? In this case, the male is XXY ...getting one X from the mother and an "XY" from the father. I know if he had the full Klinefelter's he would be infertile but, there is a mosaic variant possible in which case he would have few if any symptoms.....I know this may be a "stretch" but I was just curious if anyone on this forum might know if this is a possibility. My father had one of the distinguishing physical features....he was very tall and thin....long arms and legs.

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          • #6
            Originally posted by spanlin View Post
            Not sure if this could also be an explanation though....Could my father have had a "Mosaic" variant of Klinefelter's Syndrome? In this case, the male is XXY ...getting one X from the mother and an "XY" from the father. I know if he had the full Klinefelter's he would be infertile but, there is a mosaic variant possible in which case he would have few if any symptoms.....I know this may be a "stretch" but I was just curious if anyone on this forum might know if this is a possibility. My father had one of the distinguishing physical features....he was very tall and thin....long arms and legs.
            If your cousins are females and they match you at 4.8 and 6.6 cM, you would need about 1200 SNPs each to be relevant. That is very unlikely that you meet this threshold. It is really common to match coincidentally here especially with a female to female match. Everyone seems to be singling out the X chromosome and seeing matches right now that are identical-by-state (IBS) because FTDNA is not filtering these out. But we consumers asked for it and this was simply the fastest way to give us what we wanted. A male to female match does not have such high SNP thresholds so you might get away with fewer SNPs. We always need to know if the cousins who match you are males or females. These are very small segments even if a male cousin is involved.

            The second question about Klinefelter's is really an interesting one. About 0.1% to 0.2% of males have this condition = XXY. Many don't even know it. I don't know if the cells that carry XXY can ever have the two Xs crossover and recombine before being passed to the next generation. The two X chromosomes there could have different origins, therefore would not need to be identical. It is my understanding that these cells would be incapable of reproducing. However, the low spermatogenesis could be due to low hormones and hypogonadism rather than to the number of Xs in the cell. A mosaic Klinefelter male would most likely get the best chance of spermatogenesis from the cells that are normal, XY. But I really can't answer that question if it ever could occur.

            I have never heard of a Klinefelter male mixing his two XXs through recombination but that would be an interesting finding. Sometimes the non-disjunction of an X with a Y is caused by an inability to crossover in the pseudoautisomal regions in the first place. But that doesn't mean the X can't cross over with another X after it has brought the Y into the cell in an abnormal way. You need to ask someone who specializes in this area.

            If you think you have a recombined X from your father and you also have a sister who could be tested, that might be one way to see if you both got an entire X intact from your father that matched. My guess would be that you got the same X. If you don't have a sister, then you can't really test this hypothesis.

            Medical issues are beyond the scope of these discussions. So even though I shouldn't really be discussing it, just FYI, Marfan syndrome can also cause long arms and legs. I doubt your father had that either.

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            • #7
              Thank You!

              Thank you so much! The cousins that I match with are female (on my paternal side). I figured it was a longshot but didn't realize that these segments might be IBS. I wasn't sure how much cM would be considered significant for IBD on the "X". I do have a sister and will encourage her to test but your explanation makes sense and clears up my confusion. Thanks again

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