differences in FTDNA and GP markers

[GST]

Both Family Tree DNA and the Genographic Project use a 12 marker Y-DNA test, and I had both tests run separately. As best I can tell, they have in common 9 of the 12 markers, and each has 3 unique additional markers. I assume the FTdna 3 extra markers are better suited for recent ancestors while the GP 3 extra markers are more useful for prediciting the ancient DNA and haplogroup.

Is there anywhere to find a more complete description of the use of these markers? Would there be any value in combining them to produce a set of 15 markers, either for recent genealogy or for identifying subgroups of R1b?

Happily, I received identical results from FTdna and the GP for the 9 common markers (that was reassuring). FTdna and GP also both predicted my paternal line was R1b. I also had a 72% R1b prediction at this very cool website:
https://home.comcast.net/~whitathey/predictorinstr.htm

Thanks,
Gail

[Jim Barrett]

Gail,

It might be helpful if you told us which markers are different and what values were reported form each source.

FTDNA and GP do not report the value of 389-2 the same way. If you add your GP 389-1 and 389-2 values is the results the same as the 389-2 value reported by FTDNA? If it is then the results is the same, just reported differently.

[GST]

Oops, I'm afraid that I misread the labels, in fact, all 12 markers tested are identical in the Genographic Project and the FTDNA tests. So I assume that the Genographic Project is also providing probabilities of haplogroup membership, and that they do additional testing when they cannot assign a high probability to membership in a haplogroup based on the 12 marker test. (Also, all of the 12 marker test results were identical in the GP and FTDNA test, so it's nice to see that the results are reproducible.)