Um... you should watch "Because the Bible Tells Me So." Not to bring religion into the debate over the genetics of homosexuality, but they make a point on these "ex gays." But before I get to the movie, for those that just choose to change, well, there are many different possible explanations. What if the person was actually just bisexual? Their change in sexuality is therefore just based on a classification scheme that boxes people into two polarized alternatives: to like men or woman. What if their sexuality is actually fluid and they legitimately changed? And what if they are choosing to no longer be gay out of the fear of eternal damnation that is so often pushed on us in American culture and they really are still gay but just acting to appease others and their god? Anyway, this brings us back to the movie and the topic of conversion therapy... if it was possible for it to work, each therapist wouldn't have their own method but there would actually be A method that works.
Obviously, you are not gay...
BUT let's turn this back on you... if sexuality isn't genetic, there is a decision component or learning component to it (side note: I can tell you that I learned to be straight from the culture that I grew up in so that is out and I "decided" to deny my gay feelings until in 8th grade I realized that I was being stupid because they weren't going to change). So when did you decide to be straight? Why are you straight? Could you foresee yourself choosing to be with a same-sex partner? If not, why not?
As for genetics playing a part... in model organisms (I would hope by now that you have learned the genetic similarities between H. sapiens and other animals and how similar genes play similar roles across the animal kingdom) there are genes that when mutated switch the sexuality of the animal. Did this genetic determination just "die out" before we evolved? Or is it possible that there is some remnant of it in our species?
Ok, I didn't quote Miss Alyssa to bring prisons into this. I just wanted to bring in the topic of lesbians.
In my posts, I have been trying to spotlight and say "gay men" or "gay women." THis is because, as would be expected, the studies out there seem to show that women's and men's sexuality are different. Women tend to be more fluid. Yes, this might simply be our different acculturations but the studies of maternally passed down genetic determinants (at least the statistically probable existence of such) tend to hold more true for men than woman. They also found some marker (I want to say on like the telomere of some chromosome) on men that correlated with homosexuality but was absent in women.
The point of the last point is to say that women and men are different and this makes sense, think about it, would a set of genes more likely code for "be attracted to opposite" or "be attracted to MAN/WOMAN"? open ended commands like "opposite" seem a little odd in biology. Anyway, the paper that I read suggested that maybe men have a gene to be attracted to women and when mutated or whatnot, the men are attracted to men (or both) while the women have a set of genes that points them to men until changed and both don't have a "seek other" gene. Different genes for the sexes wouldn't be a novel idea for this system since it's present in others, too.