How many of them had children born with Tay-Sachs and other genetic diseases?
No doubt at least some of those couples DID have children with Tay-Sachs and other genetic diseases.
Being a physician, I don’t think you mean to say that Tay-Sachs and other genetic diseases were unheard of in the Jewish community before Dor Yeshorim.
(Aside from being ridiculous, it’s also a causal paradox.)
The Wolf