Its still not that cut and dry. It might be possible that a predisposition to homosexuality could be passed through genes, I honestly don't know. But this I do know. There is no such thing as a "gay" gene that actually causes a person to be gay. There are examples of monozygotic twins (identical twins) who are genetically identical growing up so one becomes gay and one is straight. If it were ALL up to biology this would not be possibile because their brains were virtually indentical at birth. Anything differences between these twins can rightly be attributed to the influence of their environment and free will (my favorite).