@Rov - No. As always, it is a little more complicated than that. Your question implies a couple of things, neither of which are accurate - That humans are like peas and that simple Mendelian inheritance patterns apply, and also that there is a single, identifiable, gay gene..
Human Sexual Orientation is more than just a simple, black and white argument between genetics vs environment. It is more complicated than that. Best evidence to date suggests that sexual orientation arises from a combination of a range of biological and environmental factors, encompassing genetic,embryonic and hormonal components. The effect of the environment, ie early years upbringing, individual choice, behavioral imprinting etc seems less clear to me, but has been acknowledged
That there is a substantial biological / genetic component has been demonstrated beyond question, with some of the indicative evidence coming from identical twin studies for example.