And how is the gene passed along since gays can't reproduce? It takes a heterosexual act to produce ALL people. So if a gay reproduces is he bisexual?
Studies of indentical twins, separated at birth, completely shreds the myth that all homosexuality is driven by genetics. In fact, most separated identical twins (twins sharing the same genetic material) are heterosexual. When there is a homosexual twin, only in a small minority of the cases are BOTH separated twins homosexual. If homosexuality was purely gene driven, there would be a greater percentage of twins where both twins report homosexual behavior.
It is clear that much human behavoir is genetically driven. However, it is clear from these studies that deviant sexual behavior is, by-and-large, learned.