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Does a SNP ever disappear when mutating

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  • Does a SNP ever disappear when mutating

    To make my question understandable giving an example will make it easier for me to ask.
    DF13 is a recently discovered SNP under L21.

    If a line of males , all of whom are L21+ DF 13 + , live in area long enough can they produce a person who loses the DF13+ to become DF13-.

    Up to now I have assumed that the SNP DF13+ would spontaneously appear in the L21 group. Leaving behind the L21’s who did not mutate.

    However as I gave this some thought it occurred to me that perhaps all the L21’s where DF13+ and a mutation occurred where this SNP was lost.

    Does this question make sense and is this possible? Can mutation of a SNP work either way?

  • #2
    The SNPs we use, like DF13 is known as UEPs (Unique-event polymorphisms). Here is what Wikipedia writes about UEPs:
    In genetic genealogy a unique-event polymorphism (UEP) is a genetic marker that corresponds to a mutation that is likely to occur so infrequently that it is believed overwhelmingly probable that all the individuals who share the marker, worldwide, will have inherited it from the same common ancestor, and the same single mutation event.
    So yes, it is theoretically possible a DF13+ person has a son who is DF13-, but it is so unlikely that we regard it as "not possible". Some SNPs have been found to mutate in several lines, like L69 which is then known as L69.1, L69.2 etc. according to where it sits in the tree. These SNPs are so unstable that they are not very useful in deep ancestry research, but might still be useful in surname projects.

    Is it possible that all L21+ were DF13+ and then a few mutated to DF13-? No. As all people above L21 are DF13- and we have kits that are L21+ DF13- it is absolutely certain that DF13 occurred in a person that was already L21+.

    -Kai

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    • #3
      There are two folks in the J Project who are positive for a downstream SNP and negative for a preceding upstream SNP.

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      • #4
        Originally posted by vinnie View Post
        There are two folks in the J Project who are positive for a downstream SNP and negative for a preceding upstream SNP.
        That would be similar to the example I gave with L69. So let's say the SNP you're describing is called X123, the new occurance would be called X123.2. If it is found in many other places as well, it will eventually be useless for deep ancestry.

        -Kai

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        • #5
          Thanks everyone. I suspected as much but wanted to be sure.

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          • #6
            The odds of a SNP reversing itself in future generations is probably about like the odds of winning the lottery, but... lotteries do have winners & I'm sure that SNPs do occasionally reverse.

            Timothy Peterman

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            • #7
              Originally posted by T E Peterman View Post
              The odds of a SNP reversing itself in future generations is probably about like the odds of winning the lottery, but... lotteries do have winners & I'm sure that SNPs do occasionally reverse.

              Timothy Peterman
              Not that I have the exact numbers, but for SNPs that are considered stable today, I believe it's more like winning the lottery every week for an entire year.

              -Kai

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              • #8
                It does happen, although very rarely. P25, for example, has been known to be somewhat unstable and to back mutate. Even in that case, though, it has happened only rarely.

                But there is no evidence for that in DF13. In fact, so far most of the DF13- guys have been found to be positive for DF63, which is parallel to DF13 and not downstream of it. If they had "back mutated" at DF13, they would be DF63-.

                Besides, among them, the DF13- guys have tested for all of the DF13+ subclades and are negative for all of them. That is true of the DF13- DF63- guys, as well. Among them, pretty much all of the DF13+ subclades are accounted for.

                If DF13 were unstable and subject to back mutations, I think we would have seen some indication by now.

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                • #9
                  Originally posted by k.o.gran View Post
                  That would be similar to the example I gave with L69. So let's say the SNP you're describing is called X123, the new occurance would be called X123.2. If it is found in many other places as well, it will eventually be useless for deep ancestry.

                  -Kai
                  The J1 SNPs involved are stable and subclade-defining; the PAs have the two members subgrouped as "parallel mutations!?".

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                  • #10
                    Originally posted by vinnie View Post
                    The J1 SNPs involved are stable and subclade-defining; the PAs have the two members subgrouped as "parallel mutations!?".
                    If they are "parallel mutations", then one should be called .1 and the other .2. If I were you, I would look up the SNP on the J draft tree and see what they're called there:
                    http://ytree.ftdna.com/index.php?nam...arent=11024115

                    -Kai

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                    • #11
                      Originally posted by k.o.gran View Post
                      If they are "parallel mutations", then one should be called .1 and the other .2. If I were you, I would look up the SNP on the J draft tree and see what they're called there:
                      http://ytree.ftdna.com/index.php?nam...arent=11024115

                      -Kai
                      I don't know if "parallel mutation" is the best description, but I'm not one of the project's admins. One person is tested L136-, and the other is tested P58-; both of those are well-established SNPs downstream of M267 and upstream of the well-established L147.1, for which they've both tested positive. Very strange..

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                      • #12
                        First, I do not know the J clade nor the admins in that project at all, so this is to be regarded as my theories. And keep in mind that I am not an expert in this field.

                        But if I were to comment, I would suspect the new L147 results are actually L147.5 and L147.6 (1 through 4 already exists). In other words, it seems this SNP is way too unstable to be of any use in deep ancestry research. If I was the admin of that project, I would present Thomas Krahn with the kit numbers of the tests you mentioned and ask his opinion.

                        -Kai

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                        • #13
                          so far most of the DF13- guys have been found to be positive for DF63, which is parallel to DF13.
                          Does having DF13+ exclude DF63 ?
                          I am shaping up to be DF13+ with no subclades.

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                          • #14
                            Originally posted by Brunetmj View Post
                            Does having DF13+ exclude DF63 ?
                            I am shaping up to be DF13+ with no subclades.
                            Yes, you are either DF13+ or DF63+. You can't be both. I happen to be DF63+, so hello there very, very, very distant cousin!

                            You are not alone looking for an SNP below DF13, we seem to have a lot of DF13* kits. Have you tried DF49? It is directly below DF13 and should be fairly big.

                            -Kai

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                            • #15
                              Have you tried DF49? It is directly below DF13 and should be fairly big.
                              I have tested negative for most of the big ones.
                              DF49,L96,Z255,Z253,DF21,DF41 were all negative

                              I recently ordered L513 , L37 and L555 as they are the only top tier SNP's left for me. Thats why I asked about DF 63 to make sure I am not missing one and thanks for putting that to rest. I am glad that SNP testing is so much faster than the rest of the various tests here!

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