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  • odd DNA matching

    On Ancestry.com persons A and B match on a certain segment on a certain chromosome (among other places) and also match relatively recently through genealogical paper research.

    On 23 my mom and I match person A on that certain segment on that certain chromosome but my dad does not. On FTDNA my dad matches person B on that certain segment on that certain chromosome but my mom and I do not.

    The segment is 16-18cM long so it's not that small.

    What do people make of this

    (also: person A is a V5 tester, we are all V4 testers; person B is a FamilyFinder tester and my parents are Geno 2.0 NG transfers and I am a MyHeritage transfer)
    Last edited by wombat; 11th November 2017, 11:07 PM.

  • #2
    Hi Wombat,

    Could you give the chromosome number and locations of that segment?

    Thanks,

    Jack

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    • #3
      Well, I guess it was just a freak and confusing coincidence.

      And B are relatively closeish cousins, something like 1/2 third cousins or something. Person A has tested only at 23andme and Ancestry and person B only at FTDNA and Ancestry.

      My mom and I match person A on a certain spot on 15 on 23andme and my dad matches person B on just about the same certain spot on 15 on FTDNA and with A and B related it seemed like it had to be that we actually all matches on that same spot on 15. (It turns out that I was wrong that they knew they both matched on the same spot on 15, apparently with Ancestry the tools don't even let you know).

      But then B uploaded to GEDMATCH and no matter how I dug, even at 200SNPs, 3cM I could find no match for my mom or I on that spot on 15 to person B and even overall at just 300 SNPS and 5cM is said we are not related to person B. So I guess it was just total crazy random luck that my mom and I are related to A and my dad is to B and both by even more crazy luck on nearly the same spot on 15, must be to opposite strands or that they (A and B) ended up not getting the same segment from their mutual in common ancestors.

      Anyway it shows the importance of both chromosome browsers, which Ancestry apparently lacks, and being able to dial in and adjust settings and that you just can't make an leaps of assumption.

      So I guess my mom and I are related to A and not B and my dad to B and not A and how we are related to them is through totally different paths. The surprising thing though is that B has a match in common who then in tern matches one whole side of my dad's matches and then another who matches on whole side of my mom's. Due to that we had been even more sure we'd end up all matching A and B on 15 the same way. But it seems something much more tangled and complicated is going on in the big puzzles we have.

      It's so weird that my dad has now twice ended matching people we'd thought my mom would and then my mom not matching them at all, etc. etc.

      Something confusing and complex is going on, but anyway there does not seem to be any matching issue going on at either 23 or FTDNA and freak chance no calls in the wrong spots, etc.

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      • #4
        wombat, was the match overlapping any of the 24.0 - 30.0 Mbp range on #15.

        Thanks,

        Jack

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        • #5
          Originally posted by georgian1950 View Post
          wombat, was the match overlapping any of the 24.0 - 30.0 Mbp range on #15.

          Thanks,

          Jack
          no, I think each of the matches is more like in roughly the 80-90 range, in fact, for my dad and person B here it is 83.9-90.8 Mbp range on #15 which it calls 16.7cM so I guess it applies a large factor to that region, GEDMATCH seems to call it 13.7cM

          and even going to 200SNPs, 3cM I can't get GEDMATCH to find any match for my mom and person B on #15 anywhere even near that at all
          Last edited by wombat; 13th November 2017, 06:14 PM.

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