Yes, they knew it was inheritance, and yes, it was the genes passed on from parent to offspring.
(it; was; the genes passed on from parent to offspring) (the genes; passed on; from parent to offspring) (they; knew; it was inheritance) Context(they knew,List([5, 14))):(it; was; inheritance)
they knew,List([5, 14))
it the genes they it
was passed on knew was
the genes passed on from parent to offspring
from parent to offspring
it was inheritance
inheritance