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Assessing Mismatch on Member

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  • Assessing Mismatch on Member

    My project is small, designed to test only people whose paper trail suggests a link to a 1715 individual (roughly 10 gens back) through his sons or grandsons. Our research is excellent and one is proven by legal documents. Three members are perfect matches at 67. A fourth has 3 mismatches at 67which has caused him to be very disappointed and has decided it rules him out completely.

    I have been encouraging him with my minimal DNA experience that these mismatches are not a big deal and that he still goes back to the same ancestor as the others - paper trail is so strong I am confident this is the case. Yes, we are not sure "which son of an ancestor" they go through but still the paperwork supports our suppositions for each member.

    The mismatches are off one value on DYS391; DYS537 and DYS557.
    I think only one is a rapidly mutating value.

    The good news I try to focus on is that ALL four of these members have the same "null" value at DYS572, fairly rare occurrence and a valuable clue - as I understand.

    Am I wrong in telling him it is no big deal - that it only makes it murkier exactly which ancestor he goes through but doesn't rule him out at all? We understand that there is no way that DNA alone and only circumstantial evidence, though strong, will "prove" anything. Yet . . .
    sure would like your input. Thank you, Barb

  • #2
    I usually am skeptical of paper-trail pedigrees that go way back in time when the estimated NPE rate is 3-4% per generation. But in your case, three mutations in 10 generations does not necessarily indicate an NPE, especially if there are common off-modal mutations. To me, the latter are more important. Some people use as a rule of thumb one mutation every 130 years (at 67 markers) so a 64/67 match back to a 1715 ancestor is on target.

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    • #3
      Assessing Mismatches

      Thank you, Paul, I feel better about this.

      While I have your attention - what is NPE and "off modal mutations" - the null - or the rapid mutating gene?

      The paper trail I am talking about refers only to historical legal documents with images. My mentor's challenge was "Read it for yourself" 20 years ago and now I'm addicted to documents (exclusive of census).

      I appreciate your comments!
      Barbara

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      • #4
        Originally posted by bjresh View Post
        Thank you, Paul, I feel better about this.

        While I have your attention - what is NPE and "off modal mutations" - the null - or the rapid mutating gene?

        The paper trail I am talking about refers only to historical legal documents with images. My mentor's challenge was "Read it for yourself" 20 years ago and now I'm addicted to documents (exclusive of census).

        I appreciate your comments!
        Barbara
        I posed the same question to Bennett not too long ago and he responded by saying a max of [email protected] is acceptable for confirming a relationship within a genealogical time frame.

        I have a few NPE in my projects but I cannot figure them out!

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        • #5
          Barb
          Here is my perspective.
          I think the null value marker maybe far more important then maybe understood.
          Once a marker, any marker mutates to a null value, it can never resort to having a value again. It must be passed down from father to sons, generation after generation as a null value marker mutation.

          I have a very similar sitution in the fact that my family also carries a null value marker, and has proven all the male descendants carry this null marker mutation. My ancestor we estimate was born around the 1670's - 1680's era and we have at most 2 mutations between 6th cousins.

          So in my mind, 3 mutations is not to distant in my mind considering the time frame you spoke of. For me a 64/67 match with the null mutation makes him a great match for you in my book.

          I have 4 different grand sons branches Y DNA tested from my immigrant ancestor, we are all a genetic match, and those of us who have tested for that null mutation, all carry the null mutation, and we view it as our calling card so to speak because there is no other family of my surname in our Y Haplo Group.

          2 or 3 mutations would actually be expected considering the genetic distance between cousins. I have paper trail proven 6th cousins whom are a 65/67 match with me, and I expected to see at least 2 to 3 mutations because we are 6th cousins.

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