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Using NON X-match strategy to Find MRCA

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  • alphavisions
    started a topic Using NON X-match strategy to Find MRCA

    Using NON X-match strategy to Find MRCA

    My mother is a match to KB as a 2nd-4th cousin in the FTDNA autosomal Family Finder match list.

    I've strategized that if KB is NOT an X-match, then I can rule out any lines that contributed X to my mother. Attached is an image of the Xlines I've ruled out because they are X-matches to my mother.

    Questions:
    1) I have ruled out the Charles G line, but I'm wondering if I should follow his father's line?
    2) Are there any major errors in this strategy that I need to correct?

    Weird Twist of Events:
    KB and I decided to upload my mother's tree to ancestry and attach KB's DNA file to it in my mother's "place" in the tree, just to see what matches came up. This resulted in a match from ancestry.com on the Mary A line!!!! But Mary A is an X-match to my mother. So how is it that FTDNA says KB and my mom are NOT X-matches, yet ancestry.com says they are? Gedmatch also says KB and my mom DO NOT match on Xchromosome.

    What am I missing?
    Attached Files

  • wombat
    replied
    Originally posted by John McCoy View Post
    Since it is indeed possible for a person to inherit a non-recombinant X chromosome from a female (and for a sibling to inherit the other homologous X chromosome!), the lack of X matches is not strong evidence for or against a particular relationship. Rather, the existence of an X match IS evidence of a relationship that follows the pattern of inheritance of the X chromosome.

    The lack of an X match may tip the odds, but I don't regard that as proof of anything.
    exactly, lack of match means nothing and you can't restrict lines of investigation

    while a match does let you restrict lines (although you could be tricked still if you matched the person along two different pathways)

    Leave a comment:


  • alphavisions
    replied
    Answer

    While using gedmatch testing on 2 nonXmatches, they gave this information about non-Xmatching which I feel comfortable confirms there is some value to nonXMatches:

    Based on X-DNA Genetic Distance, there is no relationship through the X-Chromosome. This means that the ancestry of one or both of these 2 individuals probably has one or more Father-to-son generations that has blocked the transfer of X-DNA. That eliminates possible relationship paths that do not contain father-son generations.

    Feel free to use the information as you desire.

    Leave a comment:


  • mabrams
    replied
    As an example of X non-matching....

    My mother has a third cousin, so they share a gg gm, born in 1813. So we have detailed trees and plenty of census and other records.

    My mother shares 61 cM with her third, so very reasonable.
    My mother also shares a Matching mtDNA of GD = 0 with her third cousin. So a double DNA confirmation.

    The mtDNA path coincidentally follows an X path. Although they should share some X DNA, 12 cM, they don't. Not even 1 cM. Nada. Zero.

    So not all X cousins share X DNA.
    Last edited by mabrams; 28th August 2017, 06:40 PM.

    Leave a comment:


  • MMaddi
    replied
    Originally posted by alphavisions View Post
    I know a lot of people have this same opinion, but if you use logic, pool A has Xmatches and therefore, the rest is pool B - nonXmatches. Thus, it follows that if you are not in pool A, you must be in pool B. So I think there is something here to investigate. Unless you can show us why it is not strong evidence? do you have an example?
    prairielad and ltd-jean-pull gave you real-life examples.

    While a recombination of the two x chromosomes, one from her father and the other from her mother, is what a woman usually passes on to her children, there are known cases, not just for prairielad and ltd-jean-pull, where an unrecombined x from either the the maternal grandfather or grandmother is passed on whole to the child by his/her mother. You would not know this is the case in your situation unless you have tested the maternal grandparents and their grandchildren, as prairielad has done.

    So, he knows by mapping the x segments that the maternal grandfather did not contribute any xDNA to two out of three sibling grandchildren. You don't have that information until you do the same, which is why you can't safely assume what you're assuming in this thread.
    Last edited by MMaddi; 18th August 2017, 11:02 AM.

    Leave a comment:


  • MMaddi
    replied
    Originally posted by alphavisions View Post
    Can you explain further why you think it's quite possible? Thanks!
    Because it actually happened in the real life example that ltd-jean-pull presented. And it may happen in your case as well, which is why the assumption of no matching x segments may cause you to rule out a line in which the common ancestors actually may be found.

    Leave a comment:


  • alphavisions
    replied
    Originally posted by prairielad View Post
    My third sister to same Grandparents. All sisters are full siblings.

    All follow the X inheritance path to inherit XDNA from maternal Grandfather, but only 1 of the 3 did.
    I'm not sure I follow your logic. your sisters could inherit their x from either your maternal or paternal grandparents and they did... That follows exactly the x inheritance paths. So why would this disprove a nonXmatch?

    Leave a comment:


  • alphavisions
    replied
    Originally posted by John McCoy View Post
    Since it is indeed possible for a person to inherit a non-recombinant X chromosome from a female (and for a sibling to inherit the other homologous X chromosome!), the lack of X matches is not strong evidence for or against a particular relationship. Rather, the existence of an X match IS evidence of a relationship that follows the pattern of inheritance of the X chromosome.

    The lack of an X match may tip the odds, but I don't regard that as proof of anything.
    I know a lot of people have this same opinion, but if you use logic, pool A has Xmatches and therefore, the rest is pool B - nonXmatches. Thus, it follows that if you are not in pool A, you must be in pool B. So I think there is something here to investigate. Unless you can show us why it is not strong evidence? do you have an example?

    Leave a comment:


  • alphavisions
    replied
    Originally posted by ltd-jean-pull View Post
    I may not be understanding what you are trying to do.

    A distant male relative of mine shares no X-DNA with his maternal grandmother. He received his maternal grandfather's X-chromosome.

    Using your rationale if he wasn't an X-match to your mother you would be thinking he can't be related via any line that contributed X-DNA, whereas it is quite possible the connection is via his maternal grandmother.
    Can you explain further why you think it's quite possible? Thanks!

    Leave a comment:


  • prairielad
    replied
    My third sister to same Grandparents. All sisters are full siblings.

    All follow the X inheritance path to inherit XDNA from maternal Grandfather, but only 1 of the 3 did.
    Attached Files

    Leave a comment:


  • prairielad
    replied
    Originally posted by ltd-jean-pull View Post
    I may not be understanding what you are trying to do.

    A distant male relative of mine shares no X-DNA with his maternal grandmother. He received his maternal grandfather's X-chromosome.

    Using your rationale if he wasn't an X-match to your mother you would be thinking he can't be related via any line that contributed X-DNA, whereas it is quite possible the connection is via his maternal grandmother.
    Two of my sisters do not match my maternal Grandfather on X, they match my maternal Grandmother along the full length of X (they received my mothers full maternal X only)

    They show as full base pair matching along the entire X chromosome at Gedmatch when comparing them

    So No (to alphavisions), not matching does not mean anything other then X can not be used as an aid in determining.
    Even many of the matches at FTDNA which are deemed X matches will have a high chance of being false depending on the size of segment you are looking at (segments under 7cM)
    Attached Files

    Leave a comment:


  • John McCoy
    replied
    Since it is indeed possible for a person to inherit a non-recombinant X chromosome from a female (and for a sibling to inherit the other homologous X chromosome!), the lack of X matches is not strong evidence for or against a particular relationship. Rather, the existence of an X match IS evidence of a relationship that follows the pattern of inheritance of the X chromosome.

    The lack of an X match may tip the odds, but I don't regard that as proof of anything.

    Leave a comment:


  • ltd-jean-pull
    replied
    I may not be understanding what you are trying to do.

    A distant male relative of mine shares no X-DNA with his maternal grandmother. He received his maternal grandfather's X-chromosome.

    Using your rationale if he wasn't an X-match to your mother you would be thinking he can't be related via any line that contributed X-DNA, whereas it is quite possible the connection is via his maternal grandmother.

    Leave a comment:


  • alphavisions
    replied
    Originally posted by ech124 View Post
    Within the context of FTDNA, X-DNA is not treated like the other chromosomes. I don't know how ancestry.com looks at it, but they do not have a chromosome browser so that is a big disadvantage when seeking DNA proof.

    Here is the FAQ here, so read it very carefully:


    https://www.familytreedna.com/learn/...-test-results/

    If you still want to pursue X-DNA as your primary strategy, feel free, but my suggestion is that triangulation is a better choice. That is just my opinion based on my personal experiences. If you do eventually achieve success, please let us know the steps that worked for you.
    Yes, I'm very familiar with the X inheritance pattern, which I'm using in my strategy. I had consulted a FTDNA project admin on my strategy and he thought there was validity to it...(ruling out the X-matches) but that DNA acts strangely sometimes...as we can see in the ancestry.com results I posted.

    To get back on track, I think there is validity in the my strategy, and hoping to get feedback from people who are open to the strategy, may want to test it, etc. Thanks for you input.

    Leave a comment:


  • ech124
    replied
    Within the context of FTDNA, X-DNA is not treated like the other chromosomes. I don't know how ancestry.com looks at it, but they do not have a chromosome browser so that is a big disadvantage when seeking DNA proof.

    Here is the FAQ here, so read it very carefully:


    https://www.familytreedna.com/learn/...-test-results/

    If you still want to pursue X-DNA as your primary strategy, feel free, but my suggestion is that triangulation is a better choice. That is just my opinion based on my personal experiences. If you do eventually achieve success, please let us know the steps that worked for you.
    Last edited by ech124; 17th August 2017, 02:04 PM.

    Leave a comment:

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