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Chromosome help

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  • Chromosome help


    I need some help with chromosome. I have tried to find a DNA match for a very long time, but not found a way. Can`t find a common ancestor. Soo I compared some matches I know where they are, and I see on chromosome 18 we all share the same. So that is from a common ancestor? Any tips how I can find out where too look? See picture under. Sorry I am completely new to this with chromosome.

  • #2
    The chromosome browser doesn't distinguish between matches on your father's side and matches on your mother's side, so those matches COULD be from more than one ancestor.

    Which company's chromosome browser did you use? It's not familiar to me, but I'm only on FTDNA and Gedmatch.

    If your results are at FTDNA, you can use the Matrix tool to see if those matches are also related to each other. See It's a few years old, but the principles are still the same.

    For an explanation of why the chromosome browser doesn't distinguish paternal from maternal matches, see

    Both these articles are worth reading even if you tested elsewhere.

    Have you tried contacting any of those matches? If you do, keep it simple ... and be clear about which testing company you match at, and how many cMs (or what the predicted relationship is). But be prepared for no replies

    Hope this helps


    • #3
      I believe image you posted is myHeritage triangulation browser.

      image is showing you all the matches which share that section of your chromosome 18, but you have two chromosome 18 (two of every chromosome), your maternal chromosome 18 and your paternal chromosome 18. Some of these matches will be matching you on your maternal while the others on your paternal.

      To find out which ones match each other you will have to select one and compare it to the other individually. If the segment is circled it will indicating they are matching each other also, thus sharing the same segment of DNA .
      Once you go through them all individually, you can then group them as your Parent A or your Parent B side.


      • #4
        Thanks, prairielad That's very helpful to me, too.


        • #5
          Thanks for reply I know that all matches are through my grandfather on my mother's side. I have DNA tests for most in family on heritage. Only me here on FTDNA See the picture under here. I know where 2 matches are in my tree that share common triangular segments. 4 of them also share chromosome 11, but don`t show because not all do. The 4 other USA mathes are Father-> Daughter One Niece and Cousin.

          So I have to look at the 2 matches I know then? And then see which ancestors they have the same. And then find the same in my tree, and search from there and down.

          The "unkown" path to the match I have tried to find out is that he was adopted when he was 1 year old, he does not know who the father is. But we have managed to find the mother.

          I know that my match is on his mother's side because he sent DNA test to his cousin he found and it was right. We share X-dna too, but it does not make sense when I use relationship tree projection on gedmatch.

          It was a Norwegian family that emigrated to the United States in the 1898-99.

          Anyway, thanks again
          Attached Files
          Last edited by KennethC; 17 April 2018, 04:10 PM.


          • #6
            Originally posted by KennethC View Post
            So I have to look at the 2 matches I know then? And then see which ancestors they have the same. And then find the same in my tree, and search from there and down.
            Yes. You should also use this interactive chart to see their likely relationship to you. Just enter the match's total shared cMs with you into the dot-outlined box at top centre, and the chart will show several likely relationships and the probability of each. Scroll down the page to see the coloured boxes that specify the relationship. (Remember that a cousin relationship might be upstream OR downstream of you.) Knowing the likely relationships to you will help eliminate a person in the tree who looks like the common ancestor but isn't.

            When you're trying to find a common ancestor for several matches, you might find a McGuire chart useful too ( A McGuire chart was designed for situations where you know how many cMs each match shares with each of the other matches - but it can also be used if you just know their cM match to you. You need to draw up your own McGuire chart, but there are some templates you can adapt.