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Introduction to FTDNA X-Chromosome Segment Matching

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  • Biblioteque
    replied
    snetphilie, so you say you can "inherit part of the X from your mother's father's father? Hmmm......

    Are you aware that the X has its own distinct pattern of inheritance? And it cannot pass through two successive men.

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  • KATM
    replied
    snetphilie, did you really have to post this in so many threads? It borders on spamming. You could have started one thread to discuss this topic.

    Plus, X chromosome recombination with Y chromosome is a topic that has been discussed in this thread: "Could an X-match be a Y-match?" in January 2018 (in which you posted the same comment above, as with so many other threads; did you even read that thread?). The bottom line seems to be that the two segments that might be recombined are very small, small enough not to even consider except in rare cases.

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  • snetphilie
    replied
    One thing nobody ever seems to mention is the fact that part of the X chromosome recombines with the Y Chromosome.

    So it is in fact possible for you to inherit part of your X chromosome from your mother's father's father. Your mother's father's X partially recombined with his Y, so one of your mother's X's contains a portion of her father's Y, and then her two X's recombine and you likely get some of that passed onto you.

    The same holds true for your father. Part of his X and Y recombined, so if you are male, you received part of the X he got from his mother in your Y chromosome, and of course the rest of the Y from him, but even his Y was a combination of his father's X and Y. If you are female, you still receive part of the Y that your father got from his father.

    Moral of the story is, as long as the X match doesn't filter out the part of the X that recombines with the Y, it is not a very accurate indicator of anything.

    Oh, and here's a video that shows how the X/Y recombination is different than the other chromosomes! https://www.biointeractive.org/class...n-y-chromosome

    Leave a comment:


  • Kathy Johnston
    replied
    Originally posted by hazel_ion View Post
    thank you, I have not been able to find a match on anything so far but am new to all this.

    So this means we do have a common ancestry but it would be way, way back in time.

    I was thinking it could be "noise"
    It could be noise.

    Leave a comment:


  • hazel_ion
    replied
    Originally posted by Kathy Johnston View Post
    Hazel, those segment sizes and/or SNP counts are very low. I would not expect to find a match within a genealogical time period.

    thank you, I have not been able to find a match on anything so far but am new to all this.

    So this means we do have a common ancestry but it would be way, way back in time.

    I was thinking it could be "noise"

    Leave a comment:


  • Kathy Johnston
    replied
    Hazel, those segment sizes and/or SNP counts are very low. I would not expect to find a match within a genealogical time period.

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  • hazel_ion
    replied
    Chr Start Location End Location Centimorgans (cM) SNPs
    X 2446434 4716986 11.6 331
    X 6235609 7564670 1.7 134
    X 7567246 8641567 1.7 150
    X 12108874 12647010 1.2 135
    X 14875784 17154243 2.0 276
    X 22024626 22582104 1.9 183
    X 22679353 23525712 4.2 208
    X 27759859 29163088 1.7 144
    X 30233837 31151660 1.3 148
    X 31333759 32441362 4.2 313
    X 36549638 37734602 1.7 103
    X 40626824 42587743 3.0 211
    X 45556938 47834835 4.3 303
    X 48024347 49766995 1.3 183
    X 50268888 53451302 2.3 200
    X 53888348 58252541 1.5 244
    X 95814806 96995537 1.5 139
    X 97107627 99490509 2.8 192
    X 104000146 107961898 1.1 309
    X 108904776 112003465 4.2 289
    X 116506884 118043316 1.6 203
    X 121209482 123240022 3.5 329
    X 124225707 125510522 2.0 114
    X 126698668 130055579 2.6 378
    X 131808162 133915839 2.3 185
    X 133954060 135582767 1.8 187
    X 142619865 143510430 2.4 112
    X 144087744 144814801 1.5 137
    X 145393541 146482974 2.2 161
    X 146487436 148406917 3.7 251
    X 149157975 150072647 3.2 177
    X 150861673 151928073 3.9 156
    X 152269895 154886292 2.9 399
    Largest segment = 11.6 cM
    Total of segments > 1 cM = 88.8 cM Actual.

    Leave a comment:


  • hazel_ion
    replied
    is it truly a match on X if low numbers ?

    GEDmatch.Com X-DNA Comparison

    Comparing Kit A427033 (*svespa)(M) and A061003 (*Hazel)(F)

    Minimum threshold size to be included in total = 100 SNPs
    Mismatch-bunching Limit = 50 SNPs
    Minimum segment cM to be included in total = 1.0 cM


    Chr Start Location End Location Centimorgans (cM) SNPs
    X 1984664 2875296 6.2 163
    X 12820540 13348788 2.1 107
    X 50818573 53426560 1.7 141
    X 55052282 67094485 1.3 329
    X 100053795 101784780 2.0 196
    X 109310685 111348168 2.6 147
    X 145106967 145975176 2.0 135
    X 146500671 148406917 3.7 251
    Largest segment = 6.2 cM
    Total of segments > 1 cM = 21.5 cM Actual.

    Leave a comment:


  • Kathy Johnston
    replied
    Originally posted by mjaMahé View Post
    Bonjour.

    Merci de vos réponses, mais l'histoire n'est pas très claire dans mon esprit. En effet, pourquoi ne puis-je pas localiser le chromosome X apporté par ma mère?

    Cordialement.

    manuel Mahé
    Translation:
    "Hello there,

    Thank you for your answers, but the story is not very clear in my mind. Indeed, why can I not locate the X chromosome contributed by my mother?

    Best regards.

    manual Mahe"

    ---
    Hello Manual Mahe,

    Your X chromosome is entirely from your mother, so it should be already located in you and it will be in the raw data. You have to download the X raw data separately. Your Y chromosome came from your father if you are a male.

    Did you order a test for your mother at Family Tree DNA? If so, does she match you? If she is your mother, she should match you on her X chromosome. Did you look in the section where you see Family Finder Matches? First click on "Show Full View" then "Compare in Chromosome Browser". FTDNA is still showing a couple regions of mismatching between parent and child which is in error. If you go directly to the browser, sometimes the filter does not show "Immediate Relatives" so make sure your closest matches are showing.

    The X that you have only came from your mother if you are a male. She mixes her two X chromosomes before passing one to you. The X that you received from her could be a mixture of the X coming from her mother and the X coming from her father. You can't tell which grandparent the different sections came from unless you have more information from the grandparent or a relative. Occasionally it will only come from one grandparent. The chromosome browser cannot tell which marker goes on which X chromosome in your mother. It will only show a match. If a grandmother raised you instead of a mother, that could show a non-match.

    Many males are worried when they have no X chromosome matches with other people. That is common at FTDNA. But you will always match your mother.

    I am not sure what you are asking. If you are looking for raw data, be sure you download the X chromosome and not just the autosomal DNA.

    Please clarify.
    Kathy

    Leave a comment:


  • mjaMahé
    replied
    Bonjour.

    Merci de vos réponses, mais l'histoire n'est pas très claire dans mon esprit. En effet, pourquoi ne puis-je pas localiser le chromosome X apporté par ma mère?

    Cordialement.

    manuel Mahé

    Leave a comment:


  • Kathy Johnston
    replied
    Originally posted by mjaMahé View Post
    Bonjour.

    Est-il normal que je n'ai aucun résultat lorsque je sélectionne X-Matches sur family finder?

    Cordialement.

    manuel Mahé
    Translation in English: Is it normal that I have no result when I select x-matches on family finder?

    Depending on the ethnic group, any males at FTDNA have no X results even at 1 cM. Females normally have a lot more because they have two X chromosomes. I believe females have more coincidental, identical by state matches.

    Correction, misspelling "many males" not "any males"
    Last edited by Kathy Johnston; 9th August 2014, 04:54 PM.

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  • thetick
    replied
    Originally posted by mjaMahé View Post
    Bonjour.

    Est-il normal que je n'ai aucun résultat lorsque je sélectionne X-Matches sur family finder?

    Cordialement.

    manuel Mahé
    Yikes please use English.

    Males will have less matches since males only have a single X chromosomes while females have two X chromosome. Males have a Y chromosome instead of a second X chromosome. Both males and females have two chromosomes for the autosomal chromosomes (1-22).

    Also your X line might be from an ethnic group(s) that is not highly tested for example Polynesian.
    Last edited by thetick; 6th June 2014, 09:36 PM.

    Leave a comment:


  • mjaMahé
    replied
    Pas de X-matches de trouvés.

    Bonjour.

    Est-il normal que je n'ai aucun résultat lorsque je sélectionne X-Matches sur family finder?

    Cordialement.

    manuel Mahé

    Leave a comment:


  • Tenn4ever
    replied
    Thank you Kathy.

    Leave a comment:


  • Kathy Johnston
    replied
    Originally posted by Tenn4ever View Post
    Should two full sisters match exactly on the X chromosome?
    Two full sisters should match one X chromosome from beginning to end (except perhaps at the very tips). They also usually have full matching segments where they match on both chromosomes. That is because their mother usually mixes her two X chromsomes before passing one to each daughter. The mother's X is rarely the same between the 2 daughters. The father's X is always the same. In the browser at Family Tree DNA you won't see the full matching segments. The entire segment is colored, hiding the difference between the chromosomes.

    If you upload the raw data from the two sisters to a third party site like David Pike's tool, you can visualize the double matching here:
    http://www.math.mun.ca/~dapike/FF23utils/

    There you should be able to see the segment start and end points coming from the mother listed as a double segment match.

    Leave a comment:

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