There is some evidence that Jews belonging to the Levi, Cohen and Cantor castes are descendants of early Hebrews, as they are all related. There is very little evidence that those of the Israel caste are similarly related to ancient Hebrews or to one another. In the period 200-1200 AD, there were numerous converts to Judaism in what is today Ukraine and Southern Russia, particularly among Turkic tribes, such as the Kazars.
So a genetic disease might target Palestinians and also many Jews whose ancestors lived in Palisrael.
It is one thing to try to invent a genetic disease, but another to actually succeed at it.