Well I am not sure the gene has been found for hetrosexuality but I would acertain it does exist... or a group of genes
Though there are plusses and minuses to the debate a quick precis can be found here about bilology and sexual orientation. I know it's Wiki but there is some good stuff in there for and against.
Lots of links here too
Genetics and Homosexuality research
Research is ongoing, as in the case of transsexuality, but there is growing evidence in brain sections, MRI scans, and studies of hormonal effects on gender and sexuality and outcomes on foetuses that are turning up all sorts of evidence for reasons that do not just include nurture, Nature must play a part. Homosexuality is prevalent in animals and is certainly not rare. See list of animals displaying homosexual behavior
There is no doubt whatsoever that research in this field is controversial. That does not make it unneccessary and it is in the interest of all of us for it to be resolved. I earnestly believe that science will eventually turn up unequivocal evidence for some kind of 'gay gene' and thereby vindicate fully it's expression
A caution is fine at this stage. But if scientists were afraid to stick their necks out too far I wonder where we would be as a species today? I think we need to stick our necks out with them too, but that is my unscientific opinion