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Thread: X Chromosome ethnicities?

  1. #71
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    Since we're talking about the X chromosome here, you probably are aware that as a female you inherited one copy from each parent. Since your father only has one copy -- from his mother -- your copy from him should match that copy completely.

    With your mother it's a different story. Since she has two copies, there were three possibilities for the X chromosome you inherited from her. It could be: (1) 100% from her father; (2) 100% from her mother; or (3) a recombination of both copies of her X chromosome.

    Possibility number #3 is generally the mostly likely, but both #1 and #3 occur with some regularity. For example, out of my three full sisters, one inherited a maternal X chromosome that came solely from our mother's father. The other two each inherited a maternal X chromosome that included DNA from each of our mother's parents.

    Naturally, my three sisters also inherited a paternal X chromosome. They match on this one, since it includes DNA only from our father's mother.

    What that means is, you can have X chromosome matches that your mother does not. As long as these are reasonably large segments -- say, more than 10 cM -- then the segment is almost certainly on your father's side. Smaller segments from the X chromosome are more uncertain, especially if they're shared between to women. If shared between a woman and a man, they're a little more certain; and if between two men they're more certain yet. (This is because the two men only have one X chromosome each to compare, whereas two women each have two X chromosomes to compare -- therefore increasing the chance of a match which is "identical by chance".)

    Your 20 cM match is probably large enough to be worth looking into, but if the person you match only has an autosomal match of 6 cM, then your most recent common ancestors could be somewhat distant. There are two things to remember:

    (1) Every time an X chromosome is passed on (always to a daughter), there is no other X chromosome to recombine with so it's as if it "skipped a generation".

    (2) Sometimes even a maternal X chromosome is passed on without recombination, as I mentioned above.

    If you contact your match, and they know their family tree pretty well, it might be possible to figure out the possible paths for that person's X chromosome DNA. You may also be able to figure out the path on your side.

    For example, even females can rule out one path right away: your father's father. Males can rule out two paths: both of their father's parents. Sometimes, you can rule out more. For example, my sister can not only rule out our father's father as being in her X paths, she can also rule out our mother's mother -- since we know that her maternal X chromosome is entirely from our mother's father (which also means it's entirely from his mother).

    Since your mother has also tested at 23andMe, as long as your results are linked then you should be able to look at Ancestry Composition and see where the segments are from each parent. Your results from 23andMe should probably be the most reliable you can get for now, since they're using "phased" data for you if your mother's results are linked.

    By "phased" I mean that by comparing your results to your mother's, 23andMe can tell what DNA came from each parent. Without phasing, they can't. Most other companies use unphased data -- and this applies, for example, to GEDmatch.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

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     Amber29 (06-21-2019)

  3. #72
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    Quote Originally Posted by geebee View Post
    Since we're talking about the X chromosome here, you probably are aware that as a female you inherited one copy from each parent. Since your father only has one copy -- from his mother -- your copy from him should match that copy completely.

    With your mother it's a different story. Since she has two copies, there were three possibilities for the X chromosome you inherited from her. It could be: (1) 100% from her father; (2) 100% from her mother; or (3) a recombination of both copies of her X chromosome.

    Possibility number #3 is generally the mostly likely, but both #1 and #3 occur with some regularity. For example, out of my three full sisters, one inherited a maternal X chromosome that came solely from our mother's father. The other two each inherited a maternal X chromosome that included DNA from each of our mother's parents.

    Naturally, my three sisters also inherited a paternal X chromosome. They match on this one, since it includes DNA only from our father's mother.

    What that means is, you can have X chromosome matches that your mother does not. As long as these are reasonably large segments -- say, more than 10 cM -- then the segment is almost certainly on your father's side. Smaller segments from the X chromosome are more uncertain, especially if they're shared between to women. If shared between a woman and a man, they're a little more certain; and if between two men they're more certain yet. (This is because the two men only have one X chromosome each to compare, whereas two women each have two X chromosomes to compare -- therefore increasing the chance of a match which is "identical by chance".)

    Your 20 cM match is probably large enough to be worth looking into, but if the person you match only has an autosomal match of 6 cM, then your most recent common ancestors could be somewhat distant. There are two things to remember:

    (1) Every time an X chromosome is passed on (always to a daughter), there is no other X chromosome to recombine with so it's as if it "skipped a generation".

    (2) Sometimes even a maternal X chromosome is passed on without recombination, as I mentioned above.

    If you contact your match, and they know their family tree pretty well, it might be possible to figure out the possible paths for that person's X chromosome DNA. You may also be able to figure out the path on your side.

    For example, even females can rule out one path right away: your father's father. Males can rule out two paths: both of their father's parents. Sometimes, you can rule out more. For example, my sister can not only rule out our father's father as being in her X paths, she can also rule out our mother's mother -- since we know that her maternal X chromosome is entirely from our mother's father (which also means it's entirely from his mother).

    Since your mother has also tested at 23andMe, as long as your results are linked then you should be able to look at Ancestry Composition and see where the segments are from each parent. Your results from 23andMe should probably be the most reliable you can get for now, since they're using "phased" data for you if your mother's results are linked.

    By "phased" I mean that by comparing your results to your mother's, 23andMe can tell what DNA came from each parent. Without phasing, they can't. Most other companies use unphased data -- and this applies, for example, to GEDmatch.
    Thanks for this information I am going to refer back to this as a reminder when i need this advice at the time when looking invidually for future reference - only difference is me and mum show 99% South Asian and she scores 0.4% western asian and north african - so it hasnt been entirely accurate for me to find out any segment from each chromosome. Even X chromosome shows all south asian
    Gedmatch Kits:
    MJ1661095 Myheritage
    JZ1078191 Ancestry
    HN6848975 23andme

  4. #73
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    Yes, if both of your mother's X chromosomes show as completely South Asian, then your maternal X chromosome should only be South Asian ... except, that 23andMe says that the results for people with at least one linked parent are usually a bit more accurate than for someone with no linked parent.

    So in theory, your Ancestry Composition should be a bit more accurate overall than your mother's. But, I'd still think that if your mother has only South Asian on either X, that's what you should have on your maternal X.

    For your paternal X, it's a different story. You should have on that X exactly what your father has (if he tested).

    Also, generally if a person does have a linked parent, then the top half of each pair of chromosomes should be for the mother, and the bottom half for the father (even if only one of the parents took the test). But be aware than on occasion they can still show very small segments in the wrong place. (So they think it's from the opposite parent than the one it really came from.) This doesn't happen often, but once in a while.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & another NA tribe, possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

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     Amber29 (06-21-2019)

  6. #74
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    So should i on this occasion that these specific european matches im getting was mixed with an south asian and only a south asian segment carried on with X and that how im getting these X? Because they literally show no south asian either only one did but at 4% the other ones didnt. I actually get different results 23andme doesnt break down the asian components that why i find it not accurate - atleast in the myheritage it showed me mixture and living dna and gedmatch is spot on and fits in line with dna matches.

    I was phased with my father who got 100 but even the dna matches doesnr even relate to his ancestry other than gedmatch which fits in. Hmmm

    I have found out dads x matches thankfully was able to traxe some families. But im getting my grandparenrs tests in Pakistan from FTDNA hopefully shows something for me to find out ... thanks!
    Gedmatch Kits:
    MJ1661095 Myheritage
    JZ1078191 Ancestry
    HN6848975 23andme

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     JerryS. (06-21-2019)

  8. #75
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    Double post
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