I know for sure that a "gay gene" has not been proven to exist, and that if anything the current state of research strongly points against it in males at least.
There is strong evidence for the influence of prenatal hormones in ultimate sexuality, but that has nothing to do with a "gay gene"..
Thank you. Since I posted I have found another thread on FR that is all about this subject. According to it there is no proof of a gay gene. Aloha
Here's a link to the thread about the lack of evidence for a "gay" gene, a summary put together by an alert freeper:
http://www.freerepublic.com/focus/f-news/1300464/posts