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Expecting closer Y-DNA match, 4th cousins

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  • Expecting closer Y-DNA match, 4th cousins

    I recently received results from a Y-DNA test between my uncle and a cousin. They are 4th cousins, 1x removed. I would expect them to match very closely as Y-DNA does not change much, however, at 12 markers they differ by 1 step, at 25 markers there are 3 step differences and they drop off as a match at this level in Family Tree DNA. By 36 markers there are 5 differences.

    Does this seem a bit odd?

    I was expecting the match to be much closer between 4th cousins.

  • #2
    Originally posted by astronamy7 View Post
    I recently received results from a Y-DNA test between my uncle and a cousin. They are 4th cousins, 1x removed. I would expect them to match very closely as Y-DNA does not change much, however, at 12 markers they differ by 1 step, at 25 markers there are 3 step differences and they drop off as a match at this level in Family Tree DNA. By 36 markers there are 5 differences.
    I don't understand the relationship between the three of you. You say one is an uncle and one is a cousin, then you say they are 4th cousins once removed.

    If you are A and the other two are B and C tell us the relationship between you and B, between you and C and between B and C.

    At 37 markers, what is the genetic difference between A and B, A and C and B and C?

    On which markers do the differences occur in each of the three cases? Are these three people in the same project where we can see their results? If not you might upload all three of them to Ysearch and give us the three Ysearch IDs.

    Warning: When you try to upload the results to Ysearch you may get a message telling you the upload failed. Before doing anything else check to see if the results has been uploaded. Many people report getting this error when the data has been uploaded.

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    • #3
      Originally posted by Jim Barrett View Post
      I don't understand the relationship between the three of you. You say one is an uncle and one is a cousin, then you say they are 4th cousins once removed.

      If you are A and the other two are B and C tell us the relationship between you and B, between you and C and between B and C.

      At 37 markers, what is the genetic difference between A and B, A and C and B and C?

      On which markers do the differences occur in each of the three cases? Are these three people in the same project where we can see their results? If not you might upload all three of them to Ysearch and give us the three Ysearch IDs.

      Warning: When you try to upload the results to Ysearch you may get a message telling you the upload failed. Before doing anything else check to see if the results has been uploaded. Many people report getting this error when the data has been uploaded.
      I'm a female, so I did not take the DNA test, I just manage the accounts. As stated in my post, my uncle and cousin took the test. The relationship between my uncle, who I'll call A, and the other tester, B, are 4th cousins, 1x removed. I'm a different generational level, so I was stating the relationship between them. So person A and B have 5 differences at the 37 marker level.

      The differences occur at DYS385 (the first number), DYS459 (the first number), DYS464 (the first number), CDY (both numbers).

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      • #4
        It's unusual though not impossible. Do your uncle and cousin have any closer matches at the 25 marker level?

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        • #5
          Originally posted by Dabney Carr View Post
          It's unusual though not impossible. Do your uncle and cousin have any closer matches at the 25 marker level?
          Both of them have one common person as their closest match, I'll call him C. My cousin has only done the 37 marker test, and he matches C with a genetic distance of 2 at 37 markers. My uncle has done a 67 marker test, and matches C at 67 markers with a genetic distance of 7. C is his only match at the 67 marker level.

          There is one other match on both of their lists, who shares the same unusual surname as C, so there may have been a name change in our line or theirs at some stage.

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          • #6
            So it looks like C is more closely related to your cousin and/or your uncle's line has had more mutations. What is your uncle's genetic distance at 37 markers to C?

            Also, have your uncle and cousin done the family finder tests? Do they match each other on FF? What about C?

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            • #7
              Originally posted by astronamy7 View Post
              The differences occur at DYS385 (the first number), DYS459 (the first number), DYS464 (the first number), CDY (both numbers).
              All of those are multiple-allele markers. I suspect that one of the two lineages underwent a recLOH, which causes doubling. So for example, a single recLOH could cause all these:
              DYS459 9-10 => 10-10
              DYS464 12-14-15-16 => 12-12-15-15
              CDY 34-38 => 38-38
              The important point is that all these changes should be treated as a single mutation.

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              • #8
                Originally posted by Dabney Carr View Post
                So it looks like C is more closely related to your cousin and/or your uncle's line has had more mutations. What is your uncle's genetic distance at 37 markers to C?

                Also, have your uncle and cousin done the family finder tests? Do they match each other on FF? What about C?
                Thank you, Dabney. At 37 markers, the difference between my uncle and C is 3.

                Only my mom and I have done the FF test, not my uncle, cousin, or C, but we do match other descendants from the same family line.

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                • #9
                  Originally posted by lgmayka View Post
                  All of those are multiple-allele markers. I suspect that one of the two lineages underwent a recLOH, which causes doubling. So for example, a single recLOH could cause all these:
                  DYS459 9-10 => 10-10
                  DYS464 12-14-15-16 => 12-12-15-15
                  CDY 34-38 => 38-38
                  The important point is that all these changes should be treated as a single mutation.
                  Interesting, so what looks like 5 mutations is really 1? Out of curiosity though, would FTDNA not take this into consideration with matching? We stop matching after 12 markers, but when I click on the Tip calculator and expand it out from 12 markers to 37, the likelihood of us being related within 4 generations goes from 33.5% to 83.5% despite us not being considered a match beyond 12 markers. I just found it all a bit puzzling!

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                  • #10
                    Originally posted by astronamy7 View Post
                    Interesting, so what looks like 5 mutations is really 1?
                    The DYS385 change may be a separate mutation.

                    You say that both CDY numbers differ. One of those may be a separate mutation.
                    Originally posted by astronamy7 View Post
                    Out of curiosity though, would FTDNA not take this into consideration with matching?
                    FTDNA has improved its matching algorithm over the years, but it is still a little too simplistic.

                    Comment


                    • #11
                      Originally posted by astronamy7 View Post
                      The differences occur at DYS385 (the first number), DYS459 (the first number), DYS464 (the first number), CDY (both numbers).
                      All of these markers, other than DYS459, have higher than normal mutation rates.

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