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  • Genetic Distance of '1'

    If the matches show a Genetic Distance of '1'......how many years, or generations, would that probably/possibly be?

    Thanks,

    Sarah

  • #2
    It depends on how many markers are being compared - 12, 25, 37, 67 or 111.

    An 11/12 match (genetic distance of 1) could easily indicate a common ancestor over 1,000 years ago. Or it could be two brothers or a father or son. It's similar with a 24/25 match. Both those levels of markers have low resolution for determining "time to most recent common ancestor" (TMRCA) within a small range of possible time periods.

    Matches at 37 or more markers have much better resolution, but it still is not an exact figure for TMRCA for a 36/37, 66/67 or 110/111 match. STR mutations are essentially random and TMRCA estimates based on genetic distance can only give a probability for the TMRCA, with a range indicating which is most likely.

    In other words, there's no exact answer to your question. FTDNA does have a TMRCA estimator, called TiP, which you can use to get an estimate for each match you have for the probability of TMRCA for each generation.

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    • #3
      Hi Sarah,

      It's possible to have 1 distance match on two different tests. Are you referring to mtDNA? I can't really answer your question about what the distances mean, but I also have a 1 distance match. I contacted her and her husband wrote me back and said she didn't recognize any of my surnames, but they didn't tell me anything about her line. I believe they are both in their 80s so I've set up a Google news feed for that surname, hoping I can find an obituary or another article that will be helpful.

      According to this link from FTDNA, a FMS match can go out to 550 years, but they don't break it down by distance number: https://www.familytreedna.com/learn/dna-basics/mtdna/

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      • #4
        Originally posted by Serket View Post
        Hi Sarah,

        It's possible to have 1 distance match on two different tests. Are you referring to mtDNA? I can't really answer your question about what the distances mean, but I also have a 1 distance match. I contacted her and her husband wrote me back and said she didn't recognize any of my surnames, but they didn't tell me anything about her line. I believe they are both in their 80s so I've set up a Google news feed for that surname, hoping I can find an obituary or another article that will be helpful.

        According to this link from FTDNA, a FMS match can go out to 550 years, but they don't break it down by distance number: https://www.familytreedna.com/learn/dna-basics/mtdna/
        Our family distance of 1 is back 9 fathers.

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        • #5
          Originally posted by darroll View Post
          Our family distance of 1 is back 9 fathers.
          Since you mention fathers I assume that you are talking about Y-DNA STR markers. Is that from a 67 marker test?

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          • #6
            My son and I have GD 1 on our Y111 results. While my brother is GD 0 to me. So my son is GD 1 to my brother and I.

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            • #7
              GD1

              Since DNA Y segements (DYS) mutate between father and son, it is not uncommon to have a GD-1. There are even more unusual cases. The admin of www.worldfamilies.net has a GD of 2 between himself and an uncle. There are double step mutations, rare, but they happen. The copy machine that creates STR's stutter, and sometimes it stutters such that a GD of 2 happens, or I imagine more than 1 DYS mutates.

              GD and DNA mutation rates are random, and (honestly) inexplicable. At Y67 I GD 0 to a couple of men with whom I share a common ancestor born 1682, and GD 1 to men with whom my common ancestor was born 1756.

              TMRCA is simply a probability, and is explained here: http://nitro.biosci.arizona.edu/ftdna/models.html#Basic

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              • #8
                Originally posted by WilliamFarrar View Post
                Since DNA Y segements (DYS) mutate between father and son, it is not uncommon to have a GD-1. There are even more unusual cases. The admin of www.worldfamilies.net has a GD of 2 between himself and an uncle. There are double step mutations, rare, but they happen. The copy machine that creates STR's stutter, and sometimes it stutters such that a GD of 2 happens, or I imagine more than 1 DYS mutates.

                GD and DNA mutation rates are random, and (honestly) inexplicable. At Y67 I GD 0 to a couple of men with whom I share a common ancestor born 1682, and GD 1 to men with whom my common ancestor was born 1756.

                TMRCA is simply a probability, and is explained here: http://nitro.biosci.arizona.edu/ftdna/models.html#Basic
                I had noticed from another real world example that a GD0 for a 67 marker test can go back as far as 4 generations. See fmoakes post #8 at http://forums.familytreedna.com/showthread.php?t=36922

                ShellyH reported a 65/67 match going back to 1630ish making a marker mutation every 100 - 150 years seems to be what has fit that group. See post #3 at http://forums.familytreedna.com/showthread.php?t=35648

                I have a GD1 for a 67 marker match with a person that has a tree going back 13 generations to the early 16th century and I have one going back 11 generations to the late 16th century and the trees don't have a common ancestor. We have a GD2 at 111 markers.

                My situation moves the max mutation back to about 200 years each but the number of generations in my case is about 5.5 generations per mutation out of 111 markers while in ShellyH's example the generations aren't provided. For fmoakes the generations are 4 without a mutation out of 67 markers but 111 markers aren't mentioned and no update on a 4th, 5th, and 6th cousin testing to see when a mutation occurred.

                67 markers matches should be increased to 111 markers.

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                • #9
                  Originally posted by WilliamFarrar View Post
                  Since DNA Y segements (DYS) mutate between father and son, it is not uncommon to have a GD-1. There are even more unusual cases. The admin of www.worldfamilies.net has a GD of 2 between himself and an uncle. There are double step mutations, rare, but they happen. The copy machine that creates STR's stutter, and sometimes it stutters such that a GD of 2 happens, or I imagine more than 1 DYS mutates.
                  My understanding of stutter is that it is an artifact of the amplification process in the lab and does not reflect the actual value the person has for the Y-STR marker.

                  In that case, the GD calculation would be wrong (Garbage In Garbage Out).

                  Re-testing the marker with YSeq (which has individual marker tests for about $10) may give a different reading for this marker so that you may find out the actual reading for the kit taker and his uncle yields a GD of zero.

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