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Imperfect mtDNA match

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  • Imperfect mtDNA match

    I had the full mtDNA sequence done on me and on one of my maternal aunts. She is my mother's sister.

    We matched at a genetic distance of 2. Theoretically it should have been a match at a genetic distance of 1. I realize that mutations happen, but it seems to me that this is extremely unlikely for people this closely related on the maternal line. (To clarify further, we share a maternal line. Her mother is my maternal grandmother.)

    How often does this happen?

    Any other comments?

    Thanks.

  • #2
    I don't really know for sure. I would expect that you are correct. You and your maternal aunt should have a perfect match to your mitochondrial DNA. If, for example, either she or your mother were adopted and not actually the biological child of your grandmother you would not expect you to match at all. I am not sure that the mtDNA knowledge and technology is highly advanced. For example, I am male and I have had my Y-DNA tested to the 111 marker. Apart from a paternal uncle, I don't have any Y matches closer than one person at a genetic distance of 3. He does not have the same last name as me and he does not match at all on Family Finder. I think this means that there are no people in the database that have a common ancestor along my male line. The common ancestor for that one person is likely more than 400-500 years ago. On the other hand I have hundreds of matches to my mtDNA, all with a genetic distance of 0. None of these people match me on Family Finder. This is not useful, at the moment. Maybe this technology will become more advanced in the future.

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    • #3
      Originally posted by Towler View Post
      I don't really know for sure. I would expect that you are correct. You and your maternal aunt should have a perfect match to your mitochondrial DNA. If, for example, either she or your mother were adopted and not actually the biological child of your grandmother you would not expect you to match at all. I am not sure that the mtDNA knowledge and technology is highly advanced. For example, I am male and I have had my Y-DNA tested to the 111 marker. Apart from a paternal uncle, I don't have any Y matches closer than one person at a genetic distance of 3. He does not have the same last name as me and he does not match at all on Family Finder. I think this means that there are no people in the database that have a common ancestor along my male line. The common ancestor for that one person is likely more than 400-500 years ago. On the other hand I have hundreds of matches to my mtDNA, all with a genetic distance of 0. None of these people match me on Family Finder. This is not useful, at the moment. Maybe this technology will become more advanced in the future.
      My Aunt has a close match with me in the autosomal test, and she and my mother had the same mother.

      It's always possible for a mutation to creep into the mitochondrial dna, but unlikely in such a short time.

      Regarding Y-dna, I only have two matches in the 67 marker test. Upon investigation, both are confirmed relatives, but only if we go back many generations. In addition, one actually has the same last name as mine, and the other has a last name of a family that was very closely associated with mine (a few hundred years ago) to the point that some members would use one surname or the other according to convenience, even though the two surnames have no obvious resemblance. Going back to the 37 marker level, two additional matches are picked up, and both have surnames that are known variants of my surname.

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      • #4
        I would say you would usually have a genetic distance of 0 with such a close relationship. Perhaps there was 1 mutation between you and your grandmother and 1 between your aunt and her mother.

        The important thing is whether your aunt shares the expected amount of DNA with you on the Family Finder test.

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