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Thread: A curious X-match of mine

  1. #11
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    Quote Originally Posted by C J Wyatt III View Post
    Kathy, if you were looking for X-DNA matches on GEDmatch, what parameters would you use?

    Jack Wyatt
    That is a difficult question, Jack, because male matches are so much more sensitive than female matches. I like to go above 10 cM for a female to female match and even for a male to female match. 7 cM is still a good threshold to start with. For a male to male match, a much lower cM segment can be IBD but I rarely find a common ancestor unless I also see a nice autosomal match as well.

    See http://www.isogg.org/wiki/Identical_by_descent for X matching thresholds at 23andMe.

    A lot of people are not looking at their X matches. There have been genealogists who were very surprised when they found a common ancestor with an X-only match - it usually is above 20 cM. Many of these are only seen at GEDmatch. However, my brother triangulates on an X-segment-only with two other males (above 20 cM) but I can't find the common ancestor. Even with good pedigrees, the ancestor is likely to be too distant in the past during American colonial times. The geographical areas could be correct though. The X pattern of inheritance does involve a lot of females and these are harder to trace. At least you can narrow the playing field with male matches because there are fewer lines to follow.

    Endogamous populations (e.g. Ashkenazi) are notorious for having too many matches and pile-up regions. But we even have some success stories coming from this population.

    When comparing matches, I also pay attention to the test company. You have to lower the SNP number if you are comparing V2 or V4 from 23andMe with FTDNA and AncestryDNA. Beware, because I find there are not only a lot of false negatives (because of SNP counts) but also a lot of false positives (if the cM size is too low in women). The SNP density is not great in some of these regions. I think Illumina could do a better job because there are SNPs available that are not being tested.

    Always do a one-to-one comparison when evaluating the match. I play around with the parameters but have not come to any definitive conclusions about what you should or should not use. We need more real-life success stories.
    Kathy

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  3. #12
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    paternal aunt, is: M136639
    maternal aunt is: M521083
    they are maternal first cousins.
    Yours,
    dp :-)
    If you match them and have a 23andme kit please send me a sharing invite. thanx.
    Quote Originally Posted by C J Wyatt III View Post
    David,

    Are your aunts' kits on GEDmatch? I'd like to take a look if it is possible.

    Thanks.

    Jack Wyatt
    Grace and good eure and long prosperitee. [Lydg. Mum. Goldsmiths]

    ysearch/mitosearch id: atr94 GENBANK/ENA mtDNA id: KF703542 member ISOGG

  4. #13
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    EDIT: I should mention this is all y-DNA. I have no X-matches, not even a list

    It seems you guys have a good handle on matches. Can you help me understand how close of a match some is? How many cM and SNPs is significant? I am curious because my top match on gedmatch is to a Chitrali with 4-5 generations MRCA and 18cM but not enough SNP matches, 550 I think. and the next best thing is someone who seems to be Irani, with 8.5 cM and 1595 SNPs, MRCA at 6-7 generations. Exactly the generation I am looking answers for. You think I should e-mail him? If he knows the name of his great x6 grandfather that might help me out. Then again his y-DNA is J something, so it's unlikely that any fruit will bear?

    Then there is a random match with someone in the Netherlands: 9.1cM/709 SNPs.
    A Polish guy: 8.1cM/764SNPs
    Last edited by khanabadoshi; 08-01-2015 at 05:25 PM.

  5. #14
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    Quote Originally Posted by kjjohnston View Post
    That is a difficult question, Jack, because male matches are so much more sensitive than female matches....

    Kathy
    Thanks Kathy for the detailed explanation. I'll take a close look at it and reply later. I have had a good bit of success using short segments so I will try to give my views about that.

    Do you think we should make this discussion a thread of its own?

    Jack

  6. #15
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    Quote Originally Posted by David Powell View Post
    paternal aunt, is: M136639
    maternal aunt is: M521083
    they are maternal first cousins.
    Yours,
    dp :-)
    If you match them and have a 23andme kit please send me a sharing invite. thanx.
    Thanks David.

    As you can tell by my reply to Kathy, my methodology is a bit out of the mainstream. That being said, I am seeing some X-DNA connections between my mother and your aunts. I'll try to put together an analysis later. In addition to my mother's autosomal results on Family Finder, we have tests pending with 23andMe and Ancestry DNA. Also she has mtDNA FMS pending. Her test will be my first exposure to 23andMe, but I certainly want to make her results accessible to anyone that is interested (that was the reason for the duplicate testing).

    This might seem an odd question for a post on X-DNA matching, but I'm curious how far back with confidence that you have your paternal line. I saw something in the regular autosomal comparisons that has my curiosity.

    Looking forward to continuing the discussion.

    Jack

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  8. #16
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    Quote Originally Posted by khanabadoshi View Post
    EDIT: I should mention this is all y-DNA. I have no X-matches, not even a list

    It seems you guys have a good handle on matches. Can you help me understand how close of a match some is? How many cM and SNPs is significant? I am curious because my top match on gedmatch is to a Chitrali with 4-5 generations MRCA and 18cM but not enough SNP matches, 550 I think. and the next best thing is someone who seems to be Irani, with 8.5 cM and 1595 SNPs, MRCA at 6-7 generations. Exactly the generation I am looking answers for. You think I should e-mail him? If he knows the name of his great x6 grandfather that might help me out. Then again his y-DNA is J something, so it's unlikely that any fruit will bear?

    Then there is a random match with someone in the Netherlands: 9.1cM/709 SNPs.
    A Polish guy: 8.1cM/764SNPs
    I think you meant all autosomal. You probably come from a population that is not heavily tested so you may have more difficulty finding matches. You may not get much help in pedigree building.

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  10. #17
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    [/QUOTE]: is there an IBD/IBS threshold for X segments. Would say 12cM be enough to assume that the segment is IBD?
    In other words does at least the first aunt share IBD -X- segments with foreign matches?[/QUOTE]

    12 cM match between females can be IBS or so far back that you can't find a common ancestor. But you'll never know until you look. If the geographic populations don't match at all, I tend to ignore the match unless the cM size is higher than 20 or there is an autosomal match to go along with it.

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  12. #18
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    Quote Originally Posted by C J Wyatt III View Post
    Thanks Kathy for the detailed explanation. I'll take a close look at it and reply later. I have had a good bit of success using short segments so I will try to give my views about that.

    Do you think we should make this discussion a thread of its own?

    Jack
    Feel free to start a new thread discussing segments or whatever you like.
    Kathy

  13. #19
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    Between 1730's to 1830's is the century my furtherest known genealogical ancestors were born.
    dp :-)
    Quote Originally Posted by C J Wyatt III View Post
    Thanks David.

    As you can tell by my reply to Kathy, my methodology is a bit out of the mainstream. That being said, I am seeing some X-DNA connections between my mother and your aunts. I'll try to put together an analysis later. In addition to my mother's autosomal results on Family Finder, we have tests pending with 23andMe and Ancestry DNA. Also she has mtDNA FMS pending. Her test will be my first exposure to 23andMe, but I certainly want to make her results accessible to anyone that is interested (that was the reason for the duplicate testing).

    This might seem an odd question for a post on X-DNA matching, but I'm curious how far back with confidence that you have your paternal line. I saw something in the regular autosomal comparisons that has my curiosity.

    Looking forward to continuing the discussion.

    Jack
    Grace and good eure and long prosperitee. [Lydg. Mum. Goldsmiths]

    ysearch/mitosearch id: atr94 GENBANK/ENA mtDNA id: KF703542 member ISOGG

  14. #20
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    Quote Originally Posted by kjjohnston View Post
    I think you meant all autosomal. You probably come from a population that is not heavily tested so you may have more difficulty finding matches. You may not get much help in pedigree building.
    Yes, my apologies. I meant autosomal. Thanks for the correction. Yes, matches are few and far in between, that's why when I see something actually pop up on the one-on-one I take it as significant, when in fact it probably isn't.

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