The only tribe that some scientists believe can be pinned down partially is the tribe of Levi... because of what has been called the Cohen Modal Haplotype (CMH)... which is basically a set of markers which have been commonly found among Jewish men who traditionally believe themselves to be of the priestly class of the tribe of Levi.
Other than the CMH, FamilyTreeDNA can match your DNA with the broader Jewish population who has also been tested... and will tell you if you have Jewish Ancestry... but because of the problem inherently connected to the historical fact that non-Jews have converted to Judaism, they can't truly say if your Jewish ancestors had Jewish DNA... because the DNA may reflect ancient or recent conversions.
I hope that makes sense. Personally, I think taking the DNA test was rewarding because it helped connect me to many of my more recent ancestors and even living family that I would have otherwise never met or connected with. So... far me, it was certainly worth taking the test, but ultimately that is a decision you have to make. Of course, everyone's financial situation is different too. If I were independently wealthy, I would help every person I could who was interested in Jewish or 10-Israel ancestry. =)
Regards,
Hanok
