There is no “Jewish” gene which is found exclusively in Jews. However, there are certain haplogroups that are more strongly associated with individuals of Jewish descent. If you belong to a haplogroup that is never found in Jews, then the test will conclusively show that you are definitely not Jewish. If you belong to a haplogroup that is found in Jews, then the test will not exclude you as being Jewish.
Maternal haplogroups associated with Jewish descent
The mtDNA haplogroups most commonly found in Ashkenazi Jews are K (31.9%), H (20.4%), N (10.1%), J (8.1%), HV (5.8%), U (5.8%) and T (4.8%).
Paternal haplogroups associated with Jewish descent
The Y-DNA haplogroups most commonly found in Jews are J (38%), E (20.4%), R1b (30.7%), G (9.7%), R1a (7.5%), Q (5.2%). Together, Y-DNA haplogroups J and E make up almost 60% of all Jews. In particular, haplogroup J1 is strongly associated with Cohanim/Kohanim Jews.
Which DNA ancestry test should you purchase?
DNA ancestry testing allows you to trace your ancestry along your paternal or maternal line by determining which haplogroup you belong to. A Y-DNA test will help you to trace your paternal lineage (father’s, father’s, father’s… line), and a mtDNA test will help you to trace your maternal lineage (mother’s, mother’s, mother’s….. line).