The concept of a
gene for
homosexuality does not exactly make the most sense. It seems like such a gene would work to
prevent itself from
replicating - a self-imposed
extinction.
I suppose it is possible for bisexuality, however, to be genetic. This gene would not eliminate itself, but spread just as well as not having that gene. And it is possible to imagine such a gene being succeptable to altering to the point where the same sex is preferred - or just as possible, that social influences involving this desire to categorize people so easily cause people with the gene to arbitrarily "pick" one sex to be attracted to.
Or maybe it would be something a little more, well, hidden. After all, fetal development is not a simple thing, but complex, involving a lot of steps, hormones for both the brain and the body, and such. Perhaps a gene that makes a woman more likely to have unusual hormonal releases during pregnancy, that affect a person's sexual orientation (and gender identity for that matter). It's conceivable, still genetic, but without being necessarily genetic in the person who is gay.
It would be interesting to see how, and how much, someone's genes play in determining their sexual orientation. After all, studies with identical twins seperated at birth have shown some amazing things that suggest that genes really do play a large part in who we are, what we like, and such. But not all of it, and I doubt there will ever be something as simple as being able to do a genetic test and determine "well, this child will be gay/bisexual/transgendered".
Besides, I don't think there are that many people who would abort a baby just because they're going to be gay. Large numbers of anti-gay social conservatives are also pro-life, for example, and they'd soon have to make a decision. And in some ways it might not be that horrible, after all, if the parents know ahead of time, there will be no messy coming out to do, and no worries about whether the parent will be accepting. No more gay children being disowned by closed-minded parents.
We know science though... asking them to voluntarily not search for knowledge is like asking an artist to not paint, a writer not to write, a geek to never touch a computer.
I personally don't care why the heck I am as I am. It's just a fact, just the way things are, and I can't change it. It doesn't matter if it's genetic, biological, or just a strange combination of social influences. I still can't make it go away. That's what is most important to me. It's who I am.