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3rd-5th Cousin but Not an X-match

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  • 3rd-5th Cousin but Not an X-match

    Hello,

    I am sure this question has been asked a million times, but I could not find an answer in the threads I've seen.

    What does it mean if someone is NOT an x-match to me? For example, a have a female DNA match (32cM)to me, but when I ran the x-match feature, she did not appear as a match.

    Does that mean our common ancestor is NOT in my maternal line? Or NOT in her maternal line? Or both?

    The confusing thing is -- among many things! -- that she is 100% Swedish; it is my maternal line that is Swedish. So, wouldn't we have an x-match?

    In short, how does one use the x-match feature to narrow down areas of comparison between matches?

    Again, I apologize for asking what is probably a very basic question, but I am trying to learn. Thank you for any explanations.

  • #2
    It means that in the link between you neither of you has two consecutive males.

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    • #3
      Someone will give a more scientific answer than me but just because you're not an X match doesn't mean you are not related on your maternal line. DNA is recombined and inherited randomly and the X is no exception. I don't have a link handy but I know there is a chart available somewhere than shows just how random the inheritance of DNA on the X can be as you go down the generations.

      Imagine my surprise when I tested my paternal grandmother and one of her 1st cousins. They are actually half 1st cousins through a common grandmother (my great-great-grandmother). My grandma would have received an X chromosome from her father the DNA in which he got from the common grandmother. The half 1st cousin would have inherited recombined DNA from her mother which she got from the common grandmother and her 2nd husband. My grandmother and her cousin are definitely cousins but they share absolutely nothing on the X chromosome. The X chromosome DNA from my great-great-grandmother was recombined out of the cousin's line (at least for her) over a couple generations. This is a rare occurrence but not outside the realm of possibilities. By the time one gets to 3rd-5th cousins the chances of sharing DNA on the X chromosome are smaller.

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      • #4
        Thank you both for your replies.

        So, NOT being an x-match does not rule out a relationship on the maternal line? So in this specific instance, the 3rd-5th cousin DNA match who is NOT an x-match to me, the lack of having that x-match doesn't really tell us anything at all about where our connection is?

        Again, sorry for my ignorance, but what, then, does an x-match help one determine? Does it rule out -- or indicate -- a certain line (maternal or paternal)?

        Thanks again...

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        • #5
          An X match can help you narrow down the potential paths. The most important thing to remember is that it cannot be two male generations in a row - a man does not pass an X on to a son. Men do pass on an X to a daughter.

          Roberta Estes' blog contains this post on the X chromosome: http://dna-explained.com/2012/09/27/x-marks-the-spot/. If you scroll down you'll see pedigree charts for a man and a woman and how you can narrow down potential lines. That is what I was thinking of earlier today but forgot about her blog.

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          • #6
            Thank you, andreastill. After writing earlier, I did some more digging and read a few articles on the x chromosome. Can't say I got it all 100%, but it was helpful -- I understand that it isn't a simple tool to determining the DNA path, necessarily.

            For example, if I AM an x-match with someone, that means that our relationship could lay with her mother, or her father. BUT, if my match were male, our connection could only be through his mother. Right?

            Whew! So much to learn. Though, in this instance of my 3rd-5th cousin female match (who isn't an x-match), it doesn't mean anything really in terms of where to look for our link.

            Thanks again!

            Comment


            • #7
              Originally posted by Meredith View Post
              Does it rule out -- or indicate -- a certain line (maternal or paternal)?
              When two males share a segment on the x, it says that the common ancestor is on the maternal side. That's not the maternal line, which is used when speaking of mtDNA and is the strict maternal line - mother, maternal grandmother, maternal grandmother's mother, etc. Maternal side refers to any line in the ancestry of the mother.

              When a female shares a segment on the x with anyone, the common ancestor can be either from the father's or mother's side. This is because she received an x from each of her parents.

              However, only certain ancestors contribute DNA to the x, whether in a man or woman. This is because, as referred to above, an x is not passed down through two straight male ancestors. The best way to visualize this is through diagrams of x inheritance in men and women.

              Male x inheritance - http://www.thegeneticgenealogist.com...8/12/1male.png
              Female x inheritance - http://www.thegeneticgenealogist.com...2008/12/1b.png

              The pink arcs are female ancestors who contribute DNA to a descendant's x. The blue arcs are the male ancestors who contribute DNA to descendant's x. The white arcs are ancestors who don't contribute any DNA to a descendant's x.

              If you share a segment on the x with someone, you can rule out your ancestors who are in the white arcs in the diagrams as being the common ancestor for the segment.

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              • #8
                Thank you, MMaddi! I appreciate your explanation and links. It seems to me that I will have more luck when I DO have an x-match, as opposed to NOT having one, as I do not with this specific DNA match (female). It just sounds like one can make more determinations with the x-match, as opposed to simply not having one.

                Thanks again!

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                • #9
                  @Meredith

                  Originally posted by Meredith View Post
                  Thank you, MMaddi! I appreciate your explanation and links. It seems to me that I will have more luck when I DO have an x-match, as opposed to NOT having one, as I do not with this specific DNA match (female). It just sounds like one can make more determinations with the x-match, as opposed to simply not having one.

                  Thanks again!
                  Your luck might mean that so far only those parts of your family to which you are connected via X chromosome tested here...

                  W.

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                  • #10
                    Originally posted by Meredith View Post
                    Hello,

                    I am sure this question has been asked a million times, but I could not find an answer in the threads I've seen.

                    What does it mean if someone is NOT an x-match to me? For example, a have a female DNA match (32cM)to me, but when I ran the x-match feature, she did not appear as a match.

                    Does that mean our common ancestor is NOT in my maternal line? Or NOT in her maternal line? Or both?
                    Lack of an X match does not rule out that particular line. You just may not have inherited a matching segment.

                    And women get it from both parents.

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