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Trying to locate Paternal Grandmother with X-match. Help.

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  • Trying to locate Paternal Grandmother with X-match. Help.

    Hi there. My paternal grandmother's parentage is unknown and I'd like to try to identify possible surnames in her lineage if I could. Unfortunately both my father and mother are deceased as are my paternal grandparents. The only person's DNA I can utilize to attempt this is a male paternal first cousin. I have him listed in my family tree so that Family Finder gives me Paternal matches. Several of these identified Paternal matches show matches on the X chromosome. Would those X-matches indicate probably relatives of my paternal grandmother? Thank you for any help.

  • #2
    Is this paternal 1st cousin son of your fathers sister, if so, some of his X matches ( I would only look at X matches 10cM or greater) will be through your paternal Grandmother, some will be through your paternal Grandfather. His mother had two X's, one from her father, one from her mother. He would have received a mixture of the two to form his single X.

    If he is son of your fathers brother, then he does not have an X chromosome from your paternal Grandparents lines, he received his fathers Y chromosome, not fathers X chromosome. His X will only be through his mothers lines

    You on the other hand (assume female), will have your fathers complete X, that he solely received from his mother, your paternal Grandmother.
    Note though you also have an X from your mother, so a X match can be either to your paternal Grandmother, or either of your maternal Grandparents.

    if you match on X with a match that overlaps at the same locations that your paternal 1st cousin (if he is son of your fathers sister) has with same match, then you can assume that match will be through one of your paternal Grandmothers line.
    Again only recommend using X segments over 10cM (many people recommend 20cM minimum when using X as an aide)
    Last edited by prairielad; 17th October 2018, 10:21 PM.

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    • #3
      Thank you so much for the reply. Your time is appreciated and the information is very helpful. I am indeed female and my male first cousin is the son of my father's brother. Your information helps point in some further directions to looks. Especially since I hadn't realized that an X-match may be from my father. I'll put your information to good use.

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      • #4
        Your welcome
        Don't confuse the X chromosome with mtDNA

        X is part of the 23rd chromosome pair
        Women have two X chromosomes, one from mother, one from father (XX)
        Men only have one X, one from mother, the other single chromosome 23 is the Y from father (XY)
        XDNA is inherited both through maternal and paternal lines, with the exception that males do not pass it on to sons. All Males in tree can have their fathers lines omitted when looking for common ancestor in regards to shared XDNA along with an autosomal share.

        mtDNA is a structure separate from chromosomal DNA, it is solely passed on by mothers to both sons and daughters, daughters only pass it on to next generation.
        Last edited by prairielad; 18th October 2018, 10:08 PM.

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        • #5
          To some extent, you are fortunate.... According to the math, looking for your paternal grandmother should be the most productive search for a woman and X DNA. 50% of your X DNA came from her, on the average. However the X is very unpredictable so take that 50% very casually. (Although it might be even more)

          Here is a female X DNA chart with percents... again take the percents as a very loose hypothetical. I prefer a blue/pink fan chart but I can only find it for males, so use this one
          http://freepages.rootsweb.com/~hulse...%205%20gen.pdf

          I am also looking for my maternal-paternal great grandmother (mother's father's mother), which would be the same as you if based upon my mother (whom I did test). I have not had much luck looking for her via the X. Most of my X (over 120 cM) came via my maternal grandmother, and boxes 29 and 30 (mostly 30, which is a bit uncommon if you look at the percents). So my advice to you did not work very well for me, but that's XDNA for you....

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