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I need help in interpreting the results of 3 67 marker tests

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  • I need help in interpreting the results of 3 67 marker tests

    Three of us have taken 67 marker ydna tests. We are all brickwalled on our GGgrandfather. The three great great grandfathers lived in different area but all had connections in TN. Each of us has 65/67 marker matches with each of the other test subjects but the mismatches are at different sites. the results are:

    Garry B C
    35 CDYb 39 39 38
    36 442 14 13 13
    60 446 13 12 13
    I think I should be able to infer more from these tests than the calculated probability of a common ancestor in a given generation. Are there any suggestions out there.
    thanks,
    Garry Brown

  • #2
    I guess you've tried the TiP calculator? If not, on your matches page, there should be a blue and orange icon like a family tree branch symbol in the right hand column against various names. Clicking on that invokes FTDA's TiP Calculator.

    As to its usefulness in terms of its predictions, have a read of this:

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    • #3
      Thanks.

      Thank you for the quick response. I did read the FAQ on the TIP calulator and I have used the TIP calulator. But it seems to me that in this case i have more information and should be able to glean more insight regarding our relationship than is provided by the TIP calculator. The intersection of these three tests should provide an enhanced or refined estimate. I suppose there is no way to infer from these results the order of the mutations?

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      • #4
        Originally posted by gsbrown View Post
        The intersection of these three tests should provide an enhanced or refined estimate. I suppose there is no way to infer from these results the order of the mutations?
        It might be possible. With luck, one of the heavy hitters in STR analysis might chime in.

        Although I've never tried it, FTDNA can supposedly help with such questions. Might be worth a call to them.

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        • #5
          I need help in interpreting the results of 3 67marker tests

          I agree with GTC's reply immediately preceeding this reply.

          This may or may not mirror your experience, but a cousin and I match 66/67. There have been only five actual generations between our gggf and us (including our Most Recent Common ancestor), but using the FTDNA 25 years per generation there would be 219 years or roughly 9 generations.

          I am descended from our MRCA via his first born son, William, while cousin Sam is descended via his second son, Eli. Our MRCA calculation set to show every generation shows a probability of 95.21% eight generations ago and 97% nine generations ago.

          We will go with our documentation but feel supported by the Tip calculator. I offer this to occupy your time while your are waiting to hear from FTDNA, which should only be a couple of days.
          Last edited by wmccown; 1 September 2009, 12:58 PM. Reason: typo

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          • #6
            Originally posted by wmccown View Post
            using the FTDNA 25 years per generation there would be 219 years or roughly 9 generations.
            Seeing that reminded me of a question I asked elsewhere recently on how many years should be considered a generation. The answer I got was more like 30, and I was referred to this interesting article from Ancestry Magazine: Research Cornerstones: How Long Is a Generation? Science Provides an Answer.

            Here's a link to the full article:



            and also these interesting charts from SMGF:

            The Y-chromosome is passed down almost unchanged from father to son. Males with a common parental ancestor will have almost identical DNA.


            Both men and women inherit mtDNA from their mothers who in turn pass on this genetic material down through generations of hereditary lineage.

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            • #7
              I need help in interpreting the results of 3 67marker tests

              In response to GTC, There was an FTDNA convention early this year and one of the papers dealt with the FTDNATip tool. The gist of what I have heard is that changes will be made that will generally tend to reduce the number of generations usually found when calculating the Most Recent Common Ancestor (MRCA). I don't know whether this will increase the number of years per generation used by the tool, but that would seem logical. Two FTDNA group administrators that I am aware of use probabilities of 50 to 75% to determine the likelyhood of an MRCA. They are Barry McCain, Ulster Heritage Group, and Joseph Donohoe of the Breifne Clans Group. I also have heard that FTDNA may increase the number of Y-DNA markers available for testing to as many as 100. I have no first hand information on either the changing of the tip tool or increasing the available markers. I did read the Ancestry.com link and found it interesting. I used 25 years only because that is what the tip tool currently uses.

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