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  • Brother mismatch

    Without each other's knowledge my brother and I had our DNA "tested". He went to Genebase and I, of course, to FTDNA. He did their 20 marker test and I did FTDNA's 37 marker. I have two 24 marker exact matches. We, however, have a single marker mismatch in DYS # GATA H4. He has 12 STRs and I have 11 in that DYS. Mutation, lab error, ????? Any ideas? Thanks

  • #2
    Genebase and FTDNA each test GATAH4 slightly differently, which causes Genebase's result to always be one higher than FTDNA's. So you're really an exact match when you adjust for the testing difference.

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    • #3
      I assume you know that mutations must occur. If they didn't we would all have the same results and DNA testing would be a total waste. Why shouldn't a mutation occur between you and your brother. I believe Bennett Greenspan, president of FTDNA, and his father are a genetic distance of one on the first 12 FTDNA markers.

      As has already been pointed out companies don't report all markers the same way. SMGF has a chart http://www.smgf.org/ychromosome/marker_standards.jspx show conversions. A problem with any conversion chart is the conversions change because the companies change the way they report markers.

      I think, as already reported, the conversion for GATA H4 between these two companies is 1 with. From the site above, to obtain the International Society of Forensic Genetics (ISFG) value add 10 to the FTDNA value and 9 to the Genebase value. Following these directions both of you have a ISFG value of 21.

      Isn't it nice how easy they make it for us to compare results.

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      • #4
        Thanks so much for the help. My brother has decided to do a retest at FTDNA, not so much for the difference in testing, but for the perceived better support and group dynamics.

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        • #5
          Geneseeker,

          Are you aware of the special promotion for people who tested with another company to re-test at FTDNA? Your brother can get retested at drastically lower prices than FTDNA's standard retail prices. More details here:

          http://www.familytreedna.com/PDF/PROMO_GAP.pdf

          Elise

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          • #6
            I wasn't aware, thanks again for your help.

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            • #7
              Ain't that the truth!

              Originally posted by Geneseeker View Post
              Thanks so much for the help. My brother has decided to do a retest at FTDNA, not so much for the difference in testing, but for the perceived better support and group dynamics.
              There is NOTHING perceived about it. I just wish there was a way for everyone to see the difference between companies before they order. Anyone who doesn't know FTDNA is miles ahead of the other companies needs to call each companies support line and ask a simple question.

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              • #8
                A question for you Jim..

                Originally posted by Jim Barrett View Post
                I assume you know that mutations must occur. If they didn't we would all have the same results and DNA testing would be a total waste. Why shouldn't a mutation occur between you and your brother. I believe Bennett Greenspan, president of FTDNA, and his father are a genetic distance of one on the first 12 FTDNA markers.

                As has already been pointed out companies don't report all markers the same way. SMGF has a chart http://www.smgf.org/ychromosome/marker_standards.jspx show conversions. A problem with any conversion chart is the conversions change because the companies change the way they report markers.

                I think, as already reported, the conversion for GATA H4 between these two companies is 1 with. From the site above, to obtain the International Society of Forensic Genetics (ISFG) value add 10 to the FTDNA value and 9 to the Genebase value. Following these directions both of you have a ISFG value of 21.

                Isn't it nice how easy they make it for us to compare results.
                If a mutation is possible between brothers and fathers, then would it be possible that a GD of 3 @12 markers with someone in the same surname makes it impossible to be related within a genealogical time frame?

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                • #9
                  Originally posted by Zaru View Post
                  If a mutation is possible between brothers and fathers, then would it be possible that a GD of 3 @12 markers with someone in the same surname makes it impossible to be related within a genealogical time frame?
                  I would say YES.

                  You must understand that FTDNA doesn't use "genetic distance" on the Matches pages, they use "marker differences", even though they say "genetic distance".

                  Go look at your matches at 23/25 or something like that. Each person might, and likely does, differ on different markers. Then look at the little sideways tree marker. At 23/25, the first guy on my list is 89.1% at 24 generations for a common shared ancestor. The next guy at 23/25 is 89.34% at 24 generations for a common shared ancestor.

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