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Thread: AC/Admix on the X Chromosome (doesn't match Hap)

  1. #1
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    AC/Admix on the X Chromosome (doesn't match Hap)

    Greetings!

    My X haplogroup is B2a1a. My mother's maternal family is from Mexico (so the hap isn't surprising). From what I have gathered, the recombination rate on X is relatively low and can allow for more contiguous segments. So the question is... if I have a Native American X haplogroup from a maternal ancestor from Mexico, why is 100% of the AC on that X: Northern European?

    By 23andMe's AC calc, around 60%+ of it is labeled French/German, and the rest is 'Broadly Northern Euro"... there isn't a drop of native/iberian on my X. Using a friend's profile whose maternal grandmother is also from Mexico (X Hap: D1), his AC on the X is entirely Native American & Iberian... what you might expect.

    My overall AC contains this relevant data:

    Iberian: 8.4%
    Broadly Southern Euro: 11.6%
    Native: 6.8%

    The rest of me is all Northern Euro (father, and mother's father).

    Any thoughts?
    Last edited by Unfounded; 02-10-2015 at 07:07 PM.

  2. #2
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    I should mention that I know Mexico has a more diverse genetic landscape than Iberian & American. It's just that those %'s add up to the expected 25% from my maternal grandmother. I suppose there is always the possibility that some of the S_EU is from my dad (some Bavarian) and that there is French/German admix on the mexican line. It just seems surprising that it would be so much as to take the full 50% of what a mexican woman w/ an American hap contributed to the X.
    Last edited by Unfounded; 02-10-2015 at 07:12 PM.

  3. #3
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    Sounds like your mitochondrial DNA is B2a1a. This was passed down from your all-maternal line but it is not part of the X.

    The X chromosome is inherited entirely separately from the mitochondria. Since you are male, your X chromosome comes entirely from your mother but it usually does not follow the same line as mtDNA. In terms of probability, you are much more likely to have an X chromosome that was mixed by various female ancestors but it usually also includes males in the line of descent. There simply cannot be two males in a row which means no father to son transmission. A zigzag male to female to male to female transmission is common for X segments.
    See the probability here:
    http://www.thegeneticgenealogist.com...mosome-charts/

    Your mother does not have to mix her two X chromosomes, but that is usually what happens. She can give you an X entirely from her father which has been known to happen. Most of your X probably came from him. The amount can be from 0 to 100% from each of her parents as long as she gives you one entire X made up of one or both of her two Xs. There is random slicing and splicing of these chromosomes, but often is not 50% from each one. She does not change her mtDNA at all unless there is a new mutation.

    It is very common for the admixture on the X not to match the expected geographic migration pathway of the mtDNA at all.

  4. #4
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    Thanks for your explanation, that definitely helps!

    I spoke to her last night, and she claimed that my great-grandma was french, despite being a Mexican national and my grandma claiming otherwise (gma is a bit nuts, so who knows). Either way, it sounds like it could be the off chance that I got it almost all of it from my grandpa or possibly a combination of that and the french ggma.

    I suppose the fun experiment now would be to have my mother tested to see what her X looks like.
    Last edited by Unfounded; 02-12-2015 at 01:45 PM.

  5. #5
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    Quote Originally Posted by Unfounded View Post
    Thanks for your explanation, that definitely helps!

    I spoke to her last night, and she claimed that my great-grandma was french, despite being a Mexican national and my grandma claiming otherwise (gma is a bit nuts, so who knows). Either way, it sounds like it could be the off chance that I got it almost all of it from my grandpa or possibly a combination of that and the french ggma.

    I suppose the fun experiment now would be to have my mother tested to see what her X looks like.
    23andMe is the only testing company that is attempting to give you biogeographical analysis of the X. Don't be surprised if your ancestry composition keeps changing though. Check back often. It would be interesting to test your mother. However, it appears to be difficult to break the ancestry down into local European regions even when phased. Brothers who match haplotype blocks exactly in some segments can fall into two different geographical regions depending on the adjacent markers. For example, French, German, British and Irish are hard to distinguish. Use these tests for entertainment purposes only. Continental ancestry and endogamous ancestry can often be determined but ambiguity is the norm when you try to refine it to a local region.

  6. #6
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    Quote Originally Posted by kjjohnston View Post
    23andMe is the only testing company that is attempting to give you biogeographical analysis of the X. Don't be surprised if your ancestry composition keeps changing though. Check back often. It would be interesting to test your mother. However, it appears to be difficult to break the ancestry down into local European regions even when phased. Brothers who match haplotype blocks exactly in some segments can fall into two different geographical regions depending on the adjacent markers. For example, French, German, British and Irish are hard to distinguish. Use these tests for entertainment purposes only. Continental ancestry and endogamous ancestry can often be determined but ambiguity is the norm when you try to refine it to a local region.
    Are 23andme accurate?

    my wife is stated as 100% iberian ........from galicia .........yet I have paper trail from registrars from here line and the last 250 years plus are in North-East Italy...........who old is this X chr in reagrds to 23andme?


    My Path = ( K-M9+, TL-P326+, T-M184+, L490+, M70+, PF5664+, L131+, L446+, CTS933+, CTS3767+, CTS8862+, Z19945+, Y70078+ )

  7. #7
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    Quote Originally Posted by Unfounded View Post
    Greetings!

    My X haplogroup is B2a1a. My mother's maternal family is from Mexico (so the hap isn't surprising). From what I have gathered, the recombination rate on X is relatively low and can allow for more contiguous segments. So the question is... if I have a Native American X haplogroup from a maternal ancestor from Mexico, why is 100% of the AC on that X: Northern European?

    By 23andMe's AC calc, around 60%+ of it is labeled French/German, and the rest is 'Broadly Northern Euro"... there isn't a drop of native/iberian on my X. Using a friend's profile whose maternal grandmother is also from Mexico (X Hap: D1), his AC on the X is entirely Native American & Iberian... what you might expect.

    My overall AC contains this relevant data:

    Iberian: 8.4%
    Broadly Southern Euro: 11.6%
    Native: 6.8%

    The rest of me is all Northern Euro (father, and mother's father).

    Any thoughts?
    Don't think of the X chromosome as automatically being maternal. Yes, everyone -- both males and females -- inherits an X chromosome from his or her mother. But, every human being has an X chromosome. It's just that females happen to have two.

    So what this means is that once you've gone back a few generations, your might have inherited no X chromosome DNA from your mtDNA ancestors. For example, this is true for my oldest brother and oldest sister for all ancestors beyond our mother. Obviously, both of them inherited their mtDNA from her. They also each inherited one X chromosome from her. However, our mother's mtDNA came from her mother, while the X chromosome she passed on to these two siblings of mine was entirely from her father. Therefore, neither of them has any X-chromosome DNA from the mtDNA ancestors before our mother.

    Since you're male, you only have one X chromosome which you're right to think came from your mother. But you mention the origin of your mother's maternal family. The point I'm trying to make is that you can't assume any link between your mtDNA and your X chromosome beyond your mother.

    Even if the link does continue beyond your mother, it might not continue beyond her mother, or her mother's mother. In fact, if you go back far enough the odds of any X chromosome DNA having been handed down all the way to you on that specific line actually become rather small. It's possible, of course. But the only lines you can rule out for the X chromosome are your father's, or any line involving a male-to-male DNA transmission. (Like your mother's father's father, for example. Or your mother's mother's father's father.)
    Last edited by geebee; 08-13-2019 at 04:02 PM.
    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

  8. #8
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    Quote Originally Posted by Unfounded View Post
    Thanks for your explanation, that definitely helps!

    I spoke to her last night, and she claimed that my great-grandma was french, despite being a Mexican national and my grandma claiming otherwise (gma is a bit nuts, so who knows). Either way, it sounds like it could be the off chance that I got it almost all of it from my grandpa or possibly a combination of that and the french ggma.

    I suppose the fun experiment now would be to have my mother tested to see what her X looks like.
    Again, don't limit yourself to thinking only about female ancestors as contributing to your X chromosome. Some male ancestors are also possibilities, while some female ancestors (obviously, all of your father's female ancestors) are not. This is different from your mtDNA, which runs specifically through an all-female line of ancestors.

    Notice that you wrote, "her X". Only, unlike you she does have an X. She has two -- one from each parent. So you should not only consider only the one she got from her mother, you also should consider the one she got from her father. What she passed on to you could have been from either one of them, or partly from each of them.

    Most of my own X chromosome came from my maternal grandfather, not my maternal grandmother. Only about 20 cM surrounding the centromere came from my grandmother, although I know that this part was also from my grandmother's mother. But beyond that, I don't know if it was from my grandmother's mother's mother or from her father. I can trace my mtDNA all the way back to a 6th great grandmother, but it's much more difficult to try to trace the path(s) of an X chromosome that far!

    So just remember: mtDNA always follows a path of only women. The X chromosome can go back and forth. The only time it can't be transmitted is male-to-male. You still can't ignore men, because every daughter gets an X chromosome from her father and might pass this along (in whole or in part) to either her own daughter or her son.
    Last edited by geebee; 08-13-2019 at 04:19 PM.
    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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