If your parents were both straight, and made you, where does this gay gene come from?
If you're gay, shouldn't you be unable to pass such genes along...?
recessive genes (like left-handedness, certain hair/eye colours) or a more than on gene which could lead to an increased likelihood of being gay, could be many genes that need one mutation that would lead to being gay.
much like you can have multiple colours in your hair, I for one have brown hair with red and blond highlights that only really show in the right light, and height can't be defined as just tall/short nothing suggests that sexuality has to be one of two things.
I think it's a mix of genes and and environmental factors after all there are gay people in the middle east and Africa where is it common for it to be illegal to be gay, why would someone chose to be gay if the could be arrested or killed? On the other hand from what i have read(admittedly not very much, most from high school history class textbooks and a little from things on the television so i could be very wrong) ancient Greeks saw bisexuality as being fairly normal and didn't have a problem with gay people so they had a high population of gay/bisexual people. From that it seems to me it has to be a bit of both, some people have no choice others may have a choice.
Sorry if this is bit confusing and scatter shot I've always been terrible at typing up my own thoughts though i can them write on paper more easily.