Announcement

Collapse
No announcement yet.

What affects y-dna mutation rates?

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • What affects y-dna mutation rates?

    My two year old has tossed my copy of Oppenheimer into the tub so I'll pose these questions here.

    I am and trying to get to the nexus of y-dna percentages,mutation rates and their affects.

    I am trying to understand how it would be possible for me to be related to people who are more than 2 and 3 steps away from me in a 12 marker and 8 on a 25, with our supposed shared common ancestor only 12 generations (roughly 380 years) away. Their alleles are pretty close together. Is it possible for me to be this drastically off and still be related to them within this time period?

    Cheers.

  • #2
    More Questions Than Answers!

    Lots of things effect mutation rates. As I'm sure you know they differ from marker to marker. Some markers mutate faster or slower in some families than others. One thing to remember is that mutation rates are averages so the rates in your family could be higher or lower that published rate. Of course people don't agree on what rates should be published.

    How many people are there in the group you think you are related to that have been tested? Where they all tested by the same companies? If not have you adjusted the values as required by the difference in the ways companies report values. Do the other members of this group have closer matches? Have you had anyone who is four or five generations away from you tested? If so how did you compare tho then? If not I suggest you have some of them tested.

    I know this doesn't help, but it should give you some additional things to look into.

    Comment


    • #3
      Originally posted by Jim Barrett
      Lots of things effect mutation rates. As I'm sure you know they differ from marker to marker. Some markers mutate faster or slower in some families than others. One thing to remember is that mutation rates are averages so the rates in your family could be higher or lower that published rate. Of course people don't agree on what rates should be published.

      How many people are there in the group you think you are related to that have been tested? Where they all tested by the same companies? If not have you adjusted the values as required by the difference in the ways companies report values. Do the other members of this group have closer matches? Have you had anyone who is four or five generations away from you tested? If so how did you compare tho then? If not I suggest you have some of them tested.

      I know this doesn't help, but it should give you some additional things to look into.
      Jim-

      Thanks for your response. Here is the link to the group project,all samplings were conducted by FTDNA and I am the FIRST person on the chart. I am comparing my results vs. all 6 other Matthias St.John relatives. As you will see, I am way off from all whereas they are within close proximity to each other.

      http://www.familytreedna.com/(ly1s1i45nx1p5x45lte0jtqc)/public/StJohn/index.aspx#surnames

      Matthias, the immigrant ancestor, was born circa 1603, or twelve generations ago. According to the charts that FTDNA has, I am not possibly related to them. What should I be thinking?

      Cheers.

      Comment


      • #4
        I looked at the results. I believe all of the markers you differ on, other than the first one, are all fast moving markers. I'm not sure how you are calculating generations. I come up with Matthias St. John being born over 400 years ago. At 25 years per generation that's 16 generations from you to him and 16 back to the other members.

        How closely related are the other members to each other? If you are the only one who is a distant relative this could account for you be a long way from them. Only if you have a lot of members and they are all about the same distance from each other, can you guesstimate the haplotype of the MRCA. If you had this estimate you might see that all of you have mutated about the same distance from him. Your mutations going one way and theirs going another.

        Try to find some cousins who are fourth or fifth cousins. Have them tested and then see how the results compare. I wouldn't give up on Matthias St. John yet.

        Comment


        • #5
          Originally posted by Jim Barrett
          I looked at the results. I believe all of the markers you differ on, other than the first one, are all fast moving markers. I'm not sure how you are calculating generations. I come up with Matthias St. John being born over 400 years ago. At 25 years per generation that's 16 generations from you to him and 16 back to the other members.

          How closely related are the other members to each other? If you are the only one who is a distant relative this could account for you be a long way from them. Only if you have a lot of members and they are all about the same distance from each other, can you guesstimate the haplotype of the MRCA. If you had this estimate you might see that all of you have mutated about the same distance from him. Your mutations going one way and theirs going another.

          Try to find some cousins who are fourth or fifth cousins. Have them tested and then see how the results compare. I wouldn't give up on Matthias St. John yet.
          My calculations of generations is based on historical evidence, vis a vis birth records going back from myself to each direct male ancestor to Matthias (who was born in 1602/3).

          I don't understand the chart that FTDNA has listed then. At a genetic distance of 2 or 3 in a twelve marker I would not be related-in all likelihood they are no more or less than 2 generations from myself. In the 25 marker, I am 8 in distance and according to FTDNA it's impossible that I am related to them.

          Am I misunderstanding the charts?

          Thank you for your help!

          Cheers.
          Last edited by SaintManx; 19 November 2006, 09:38 PM. Reason: add info.

          Comment


          • #6
            I looked at my own case. When I compare myself to a person who is a genetic distance of 8 from me on 25 markers their FTDNATip calculator gives a "probability" of only 1.06% that I share a common ancestor with that person within 12 generations.

            Two things to consider here. 1) I don't believe their calculator takes into account that all but one of the differences are on fast mutating markers. 2) They are working with averages. That is all they can work with, but most people aren't average.

            Of the six other people in the group, how closely related are they? Do you have someone in the group who is a fifth cousin or closer?

            Comment


            • #7
              Originally posted by Jim Barrett
              I looked at my own case. When I compare myself to a person who is a genetic distance of 8 from me on 25 markers their FTDNATip calculator gives a "probability" of only 1.06% that I share a common ancestor with that person within 12 generations.

              Two things to consider here. 1) I don't believe their calculator takes into account that all but one of the differences are on fast mutating markers. 2) They are working with averages. That is all they can work with, but most people aren't average.

              Of the six other people in the group, how closely related are they? Do you have someone in the group who is a fifth cousin or closer?
              This is the exact chart that I was referring to:

              http://www.familytreedna.com/dna101.html

              I am in contact with the PA of the group to see how distant they may be. According to vineviz the rule of thumb is one mutation per eight generations or, every 250 years. If we used that mathematic equation, a gen. diff. of two would be a mrca at 500 years, I think-but really, 12 markers do not tell us much. Of the folks who did test 25, both were a gen. diff. of 8 from me-which would seem almost impossible-no?

              Should FTDNA clarify their findings?

              cheers again...

              Comment


              • #8
                Looking only at the DNA, I'd say that you've got several "founders" in this project.

                The haplogroup I folks are all clearly closely related.

                I'd say that 65281 and 29384 had a common ancestor 10-15 generations ago, but are not closely related to the descendants of Matthias.

                I'd say that 10181, N19542, and 73130 represent one branch of descendants from Matthias (these guys all have DYS439=12) whereas 00360, 10169, 17467, and 10177 represent a second branch (and all have DYS439=11)

                I'd say that 72248 (is that you?) might be related to Matthias, but did not descend from him (again, looking only at the DNA). 72248 misses the modal of the Matthias 7 at eight markers, and one of them (DYS449) by a distance of 3. It is not inconceivable that you could accumulate that many mutations in twelve generations, but I'd say it is VERY unlikely.

                I built a simple phylogenetic tree, based only on the twelve markers all the R1b men share. I drew my conclusions mainly from it. I'm attaching copy in PDF form (the scale at the bottom is generations). You can read it like a family tree, so to speak, but for the genes instead of the people and with the common ancestor on the left.
                Attached Files
                Last edited by vineviz; 19 November 2006, 11:08 PM.

                Comment


                • #9
                  Originally posted by vineviz
                  Looking only at the DNA, I'd say that you've got several "founders" in this project.

                  The haplogroup I folks are all clearly closely related.

                  I'd say that 65281 and 29384 had a common ancestor 10-15 generations ago, but are not closely related to the descendants of Matthias.

                  I'd say that 10181, N19542, and 73130 represent one branch of descendants from Matthias (these guys all have DYS439=12) whereas 00360, 10169, 17467, and 10177 represent a second branch (and all have DYS439=11)

                  I'd say that 72248 (is that you?) might be related to Matthias, but did not descend from him (again, looking only at the DNA). 72248 misses the modal of the Matthias 7 at eight markers, and one of them (DYS449) by a distance of 3. It is not inconceivable that you could accumulate that many mutations in twelve generations, but I'd say it is VERY unlikely.

                  I built a simple phylogenetic tree, based only on the twelve markers all the R1b men share. I drew my conclusions mainly from it. I'm attaching copy in PDF form (the scale at the bottom is generations). You can read it like a family tree, so to speak, but for the genes instead of the people and with the common ancestor on the left.
                  Thanks for responding, I was secretly hoping that you would as well as Jim and some other very informed people.

                  Some background about myself-

                  My birth certificate said St.John, I was told by family members that I was a son to someone else who is now deceased (Castronovo)-I changed my name after college graduation. For obvious reasons my mother and "father" aren't speaking about it. I am trying to confirm this in a very roundabout way. Even if my "father" is indeed my father, our paper trails lead us into a direct descendancy with Matthias. If he is not, then that would explain the difference. But if he is and I am indeed a St.John (and I have personally researched this line extensively) then I have to become even more open minded to the possibilities. Or, science cannot explain the fast mutations.

                  The project consists of four english St.Johns(I) who we were hoping to match up with Matthias-but it's obvious that they are not a match. 6 descendants of Matthias who perfectly match each other, one french descendant who perfectly matches Matthias, an Irish St.John who matches no one, and myself, who matches no one. I believe that the six descendants of Matthias arrive from three different lines of descendancy. This demonstrates enough variety and shows a cumulative equality amongst each other.

                  I find it so very difficult to believe that I am a part of this family as a result of this test. Since they all match at 12 markers, could one safely assume, since they have the same surname, that they would match at 25?

                  I am confused about how I should move at this point since my "father" laughs at science and this project in particular- I am beginning to think that it will expose the truth. Or perhaps a truth about his mother/father. I need to match up with his dna to truly know.

                  Any light would be appreciated.

                  Cheers.

                  Comment

                  Working...
                  X