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Thread: X Chromosome ethnicities?

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    Quote Originally Posted by JerryS. View Post
    right, I know that my X comes from my mom who is not related to my cousin in any fashion, while both of her's [my cousin] come from her dad [my uncle] and mom. just as her X comes from her dad [my uncle] via his mom [our grandma], both of whom I am related but do not share any X. while my Y comes from my dad [my cousin's uncle] via his dad [our grandpa] which she does not share any Y with. that was never in question. what I was asking is how much more of our grandma's DNA will my cousin have over me since she [grandma] passed down her X to her which I did not get.
    I'm not sure what you're asking. Obviously, you know that you received 0% of your paternal grandmother's two X chromosomes. Your cousin, since she is also paternally related to this grandmother, received 50% of the grandmother's two X chromosomes -- the same 50% that her father received. [But note that 50% of your grandmother's two X chromosomes is equivalent to 100% of your cousin's paternal X chromosome -- so your cousin received one entire X chromosome more from your grandmother than you did, since you received none.)

    What we don't know at this point is how much of that came from your grandmother's father and how much came from your grandmother's mother. It's possible that your cousin's X chromosome is entirely from just one of your grandmother's parents. But whatever the case, your cousin received a complete X chromosome from her paternal grandmother, versus no paternal X for you.

    As I mentioned in another post, two of my mother's six offspring inherited a maternal X chromosome that is 100% from her father. The other four inherited a maternal X chromosome that's a recombination of both of our mother's X chromosomes. My sisters, of course, also inherited identical copies of our father's only X chromosome.
    Last edited by geebee; 05-12-2019 at 06:41 AM.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

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    Quote Originally Posted by geebee View Post
    I'm not sure what you're asking. Obviously, you know that you received 0% of your paternal grandmother's two X chromosomes. Your cousin, since she is also paternally related to this grandmother, received 50% of the grandmother's two X chromosomes -- the same 50% that her father received. [But note that 50% of your grandmother's two X chromosomes is equivalent to 100% of your cousin's paternal X chromosome -- so your cousin received one entire X chromosome more from your grandmother than you did, since you received none.)

    What we don't know at this point is how much of that came from your grandmother's father and how much came from your grandmother's mother. It's possible that your cousin's X chromosome is entirely from just one of your grandmother's parents. But whatever the case, your cousin received a complete X chromosome from her paternal grandmother, versus no paternal X for you.

    As I mentioned in another post, two of my mother's six offspring inherited a maternal X chromosome that is 100% from her father. The other four inherited a maternal X chromosome that's a recombination of both of our mother's X chromosomes. My sisters, of course, also inherited identical copies of our father's only X chromosome.
    I know my cousin received some of our grandmother's X and I received none. I'm just wondering how much influence my grandma's X had on my father's Y which I got.

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    Quote Originally Posted by JerryS. View Post
    I know my cousin received some of our grandmother's X and I received none. I'm just wondering how much influence my grandma's X had on my father's Y which I got.
    Is this what you are asking?
    The pseudoautosomal regions (PAR1 and PAR2) are short regions of homology between the mammalian X and Y chromosomes. The PAR behave like an autosome and recombine during meiosis. Thus genes in this region are inherited in an autosomal rather than a strictly sex-linked fashion.

    PAR1 comprises 2.6 Mb of the short-arm tips of both X and Y chromosomes in humans and other great apes [7, 8] and is required for pairing of the X and Y chromosomes during male meiosis. All characterized genes within PAR1 escape X inactivation. X-Y pairing in the PAR is thought to serve a critical function in spermatogenesis, at least in humans and mouse [9–11]. PAR2 is located at the tips of the long arms and is a much shorter region, spanning only 320 kb [12]. PAR2 exhibits a much lower frequency of pairing and recombination than PAR1 and is not necessary for fertility [13–15].
    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2435358/
    Maternal Grandfather's Y Line: J-ZS1711
    Paternal Grandmother’s mtDNA: U5a1

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    Quote Originally Posted by Táltos View Post
    sister, you really went over my head with that one. LOL. but, I think if I decoded that, yeah. how much of my father's Y is/was effected by his mother's X and how much of that would I have gotten, generally speaking of course. in other words, how much of my paternal grandma's ethnicity did I inherit, generally speaking?

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    Quote Originally Posted by JerryS. View Post
    I know my cousin received some of our grandmother's X and I received none. I'm just wondering how much influence my grandma's X had on my father's Y which I got.
    Your grandma's X had no influence on your father's Y. His Y chromosome came 100% from his father, and therefore could have had no influence from his mother. But I suppose what you're really asking is how much influence your father's X chromosome -- which, of course, did come from his mother -- might have had on the Y chromosome he passed on to you.

    The answer is, not much. The only places where your father's X and Y chromosomes could have recombined are at the tips of the chromosomes. So, your father might have passed on to you a Y chromosome that contained a little bit of his X chromosome in these locations.

    The locations are PAR1 and PAR2, where PAR stands for "pseudoautosomal recombining region". From memory, PAR1 is something like 1.6 cM in length [it's 2.6 cM; my memory was off], and PAR2 is only about 0.32 cM in length. 23andMe does test some SNPs in each of these regions, but they report both SNPs at each location (one on the X chromosome and one on the Y chromosome) as if these SNPs were only on the X chromosome. After all, that's how they would be in women -- the SNPs from PAR1 and PAR2 would be on the two X chromosomes.

    In men, of course, one SNP at each tested location in PAR1 and PAR2 would actually be on the X chromosome, and one would be on the Y chromosome. You might in some cases be able to figure out which is which if either your father or your mother has tested. The trouble is, I don't see how you could determine which SNP came originally from your father's X chromosome and which came from his Y chromosome unless one of his parents tested.

    Of course, for any location that is homozygous for either you or your father (if you've both tested), you can tell which SNP you must have inherited from your father. But if both of you are heterozygous at a given location, you won't be able to tell which SNP came from which parent. And again, even if you can figure out which came from your father -- you'd still have to figure out if it came from his X chromosome or his Y chromosome.

    As I said, though, the contribution from your grandmother can't be much in any case. At most, your father's contribution at PAR1 (2.6 cM max) and his contribution at PAR2 (0.32 cM max) could be from his X chromosome.

    EDIT: Found my source and corrected the amount for PAR1. https://en.wikipedia.org/wiki/Pseudoautosomal_region
    Last edited by geebee; 05-14-2019 at 02:32 PM.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

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    Quote Originally Posted by JerryS. View Post
    sister, you really went over my head with that one. LOL. but, I think if I decoded that, yeah. how much of my father's Y is/was effected by his mother's X and how much of that would I have gotten, generally speaking of course. in other words, how much of my paternal grandma's ethnicity did I inherit, generally speaking?
    It's always possible that you inherited more DNA from your paternal grandma than from any other parent -- but not from her X chromosome. Your father inherited an entire X chromosome from her, but he didn't pass it on to you -- other than (possibly) at those tips I mentioned.

    However, you did inherit autosomal DNA from your father's mother. I don't think you're likely to be able to figure out just how much, unless either of your paternal grandparents has been or could be tested. Or, you might possibly be able to figure it out if you have cousins who are only on her side. Whatever you share with them is likely to be in a region that came from her.

    For example, I can identify several segments that must have come from my paternal grandmother because I share these segments with several half 2nd cousins on my grandmother's father's side. They are not, as far as I can tell, related to me in any other way.

    When it comes to my X chromosome, I know that all but 20 cM of it is from my maternal grandfather (and therefore his mother). The "extra" SNPs on my X chromosome -- since I actually only have one copy -- must be from my Y chromosome, even though they're reported with the X. But they're too small to have much -- if any -- impact on the ancestry painting of my X chromosome.

    In a way, the most accurate way of depicting men's X chromosomes in Ancestry Composition would be to report one whole chromosome and two fragments of a second X chromosome. Or maybe just one fractment, PAR1, since 23andMe does report some segments of 2.6 cM in length. I don't think 0.32 cM would even register.

    Of course, the Y chromosome is not even used in Ancestry Composition, possibly because it undergoes no recombination. I say that in spite of knowing that it does recombine, at PAR1 and PAR2; but remember that these ends are not included with the Y at most companies -- but with the X. So what is reported as your Y chromosome is actually a truncated version, without the very tips (PAR1 and PAR2).

    But the bottom line is that for the purpose of determining the "ethnic origins" of your X chromosome, it doesn't point to anyone but your mother and her ancestors, even though you could have a tiny input from your father here. The input won't be to the X you received from your mother, of course, but in the two PAR regions you effectively have a 2nd X chromosome -- though it doesn't appear in the painting.

    If an ancestry painting is affected at all -- regardless of whether it's at 23andMe or elsewhere -- it has to be pretty negligible. I suspect, undetectible.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

    GB

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    Quote Originally Posted by geebee View Post
    It's always possible that you inherited more DNA from your paternal grandma than from any other parent -- but not from her X chromosome. Your father inherited an entire X chromosome from her, but he didn't pass it on to you -- other than (possibly) at those tips I mentioned.

    However, you did inherit autosomal DNA from your father's mother. I don't think you're likely to be able to figure out just how much, unless either of your paternal grandparents has been or could be tested. Or, you might possibly be able to figure it out if you have cousins who are only on her side. Whatever you share with them is likely to be in a region that came from her.

    For example, I can identify several segments that must have come from my paternal grandmother because I share these segments with several half 2nd cousins on my grandmother's father's side. They are not, as far as I can tell, related to me in any other way.

    When it comes to my X chromosome, I know that all but 20 cM of it is from my maternal grandfather (and therefore his mother). The "extra" SNPs on my X chromosome -- since I actually only have one copy -- must be from my Y chromosome, even though they're reported with the X. But they're too small to have much -- if any -- impact on the ancestry painting of my X chromosome.

    In a way, the most accurate way of depicting men's X chromosomes in Ancestry Composition would be to report one whole chromosome and two fragments of a second X chromosome. Or maybe just one fractment, PAR1, since 23andMe does report some segments of 2.6 cM in length. I don't think 0.32 cM would even register.

    Of course, the Y chromosome is not even used in Ancestry Composition, possibly because it undergoes no recombination. I say that in spite of knowing that it does recombine, at PAR1 and PAR2; but remember that these ends are not included with the Y at most companies -- but with the X. So what is reported as your Y chromosome is actually a truncated version, without the very tips (PAR1 and PAR2).

    But the bottom line is that for the purpose of determining the "ethnic origins" of your X chromosome, it doesn't point to anyone but your mother and her ancestors, even though you could have a tiny input from your father here. The input won't be to the X you received from your mother, of course, but in the two PAR regions you effectively have a 2nd X chromosome -- though it doesn't appear in the painting.

    If an ancestry painting is affected at all -- regardless of whether it's at 23andMe or elsewhere -- it has to be pretty negligible. I suspect, undetectible.
    that said, I did however receive abut 25% on my autosomal DNA from her, correct?

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    Quote Originally Posted by JerryS. View Post
    that said, I did however receive abut 25% on my autosomal DNA from her, correct?
    Yeah, that's likely. Or, say, something between about 20-30%. The total contribution of each pair of grandparents has to equal the contribution of the parent on that side, but in theory for each grandparent it could be anything from 0-50%. However, I doubt that anyone's ever actually seen a case in which a grandparent contributed either 0 or 50% to a grandchild. It would require every single chromosome from one parent to be passed on with no recombination, and all from the same grandparent. (So obviously the other grandparent would contribute nothing.)

    However, it routinely happens that a few chromosomes will be passed on from one grandparent or another, with no contribution from the opposite grandparent. For example, my father and daughter share across the entirety of chromosomes 9 and 21; and they share no part of chromosomes 7, 15, 17, 18, 22, or -- of course -- the X chromosome. So my daughter's paternal copy of chromosomes 9 and 21 are the same as my paternal copy of these chromosomes; and her paternal copy of chromosomes 7, 15, 18, 22, and the X chromosome are the same as my maternal copy of each of these. (Of course, with the X I only have a maternal copy.)

    My father has four other tested grandchildren, so I can see that my daughter is not the only one of his grandchildren to inherit some apparently "unrecombined" chromosomes. For example, my brother's son inherited all (or very nearly all; it's difficult to be sure) of my father's chromosomes 3 and 7. He inherited nothing from my father's chromosomes 4, 9, 12, 13, 18, 19, 21, or his X chromosome.

    In terms of percentages, here are the percentages each tested grandchild received from my father:

    [indent]My oldest brother's daughter -- 25.4%
    His son -- 18.5%

    My oldest sister's daughter -- 20.4%
    Her son -- 28.0%

    My daughter -- 22.5%

    By this you can actually see that only one of the five inherited within a percent of 25%. One grandson inherited even less than the 20% I mentioned above, so obviously these aren't hard and fast numbers. There are parents who have very low crossover rates, which could result in a grandchild inheriting either a very high or very low percentage from the parent's parents. In fact, if they inherit a low percentage from one, they'll necessarily inherit a high percentage from the other -- because the total has to add up to 50%.

    As a "bonus", I'll also tell you about my dad's sharing with his tested great grandson -- the son of my sister's daughter. The shared amount is 7.34%, which is a lot lower than the "expected" 12.5% for great grandparents. My sister's sharing with her grandson is not 25%, but actually only 21.5%. So presumably he shares more DNA with his mother's father, since the total should add up to 50%.

    Obviously, my parents' total contribution to their great grandson's DNA has to equal my sister's contribution, so my mother's contribution should be equal to 21.5% minus my father's contribution of 7.34%, or 14.16%. In other words, my sister's grandson inherited almost twice as much DNA from his maternal grandmother's mother as he did from his maternal grandmother's father.

    The bottom line is, you almost certainly inherited something close to 25% from your grandmother, but you can see that it could be anything from a bit less than 20% to a bit over 30%. In fact, I'll revise my 20%-30% to maybe 15-35%, which some exceptional cases that fall even outside this range. But again, both grandparents on a side together will contribute 50%.
    Last edited by geebee; Yesterday at 04:38 AM.
    Besides British-German-Catalan, ancestry includes smaller amounts of French, Irish, Swiss, Choctaw & possibly Catawba. Avatar picture is: my father, his father, & his father's father; baby is my eldest brother.

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    Quote Originally Posted by geebee View Post
    Yeah, that's likely. Or, say, something between about 20-30%. The total contribution of each pair of grandparents has to equal the contribution of the parent on that side, but in theory for each grandparent it could be anything from 0-50%. However, I doubt that anyone's ever actually seen a case in which a grandparent contributed either 0 or 50% to a grandchild. It would require every single chromosome from one parent to be passed on with no recombination, and all from the same grandparent. (So obviously the other grandparent would contribute nothing.)

    However, it routinely happens that a few chromosomes will be passed on from one grandparent or another, with no contribution from the opposite grandparent. For example, my father and daughter share across the entirety of chromosomes 9 and 21; and they share no part of chromosomes 7, 15, 17, 18, 22, or -- of course -- the X chromosome. So my daughter's paternal copy of chromosomes 9 and 21 are the same as my paternal copy of these chromosomes; and her paternal copy of chromosomes 7, 15, 18, 22, and the X chromosome are the same as my maternal copy of each of these. (Of course, with the X I only have a maternal copy.)

    My father has four other tested grandchildren, so I can see that my daughter is not the only one of his grandchildren to inherit some apparently "unrecombined" chromosomes. For example, my brother's son inherited all (or very nearly all; it's difficult to be sure) of my father's chromosomes 3 and 7. He inherited nothing from my father's chromosomes 4, 9, 12, 13, 18, 19, 21, or his X chromosome.

    In terms of percentages, here are the percentages each tested grandchild received from my father:

    [indent]My oldest brother's daughter -- 25.4%
    His son -- 18.5%

    My oldest sister's daughter -- 20.4%
    Her son -- 28.0%

    My daughter -- 22.5%

    By this you can actually see that only one of the five inherited within a percent of 25%. One grandson inherited even less than the 20% I mentioned above, so obviously these aren't hard and fast numbers. There are parents who have very low crossover rates, which could result in a grandchild inheriting either a very high or very low percentage from the parent's parents. In fact, if they inherit a low percentage from one, they'll necessarily inherit a high percentage from the other -- because the total has to add up to 50%.

    As a "bonus", I'll also tell you about my dad's sharing with his tested great grandson -- the son of my sister's daughter. The shared amount is 7.34%, which is a lot lower than the "expected" 12.5% for great grandparents. My sister's sharing with her grandson is not 25%, but actually only 21.5%. So presumably he shares more DNA with his mother's father, since the total should add up to 50%.

    Obviously, my parents' total contribution to their great grandson's DNA has to equal my sister's contribution, so my mother's contribution should be equal to 21.5% minus my father's contribution of 7.34%, or 14.16%. In other words, my sister's grandson inherited almost twice as much DNA from his maternal grandmother's mother as he did from his maternal grandmother's father.

    The bottom line is, you almost certainly inherited something close to 25% from your grandmother, but you can see that it could be anything from a bit less than 20% to a bit over 30%. In fact, I'll revise my 20%-30% to maybe 15-35%, which some exceptional cases that fall even outside this range. But again, both grandparents on a side together will contribute 50%.

    this really explains it well. thank you so much for this as well as the real world examples you've given. so (not always but usually) if I inherit 25% of my DNA from my grandmother and she was 25% white and 75% black I would be 18.75% black? (just using the strict math) she wasn't and I'm not but just using that as an example to simplify this...
    Last edited by JerryS.; Yesterday at 06:09 PM.

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