If people are born gay, then where is the 'gay gene'

Scientists know what genes make us what we are. They know which ones determine our sex, male or female, which ones determine our hair color, eye color, ear size, foot size, or immunity ability. Why can't they find the 'gay gene'? How can a gene determine how a person "feels" about another person? How does a gene determine a person's 'desires'? How can that which is set and coded determine the actions of that which is not set and not coded (how can the molecule combination of H2O determine the temperature of the water?) It is my determination that it cannot (it takes outside influences to determine the temp of the water, just as it is outside influences that determine the sexual desires of a person.) There is no scientific evidence I know of that shows otherwise.

Am I correct? And if not, please show me the evidence to prove I am wrong. I don't want opinions, I prefer proven facts, if there are any.

PS. Just for the record, I know I am opening up a firestorm of rejection and assault. I am not trying to mock anyone, I would just really like to know the facts. For the sake of discussion, please be respectful.

People are not born gay, we chose to be gay. There are no gay genes.

This question makes the fallacious assumption that all traits at birth are genetic; it is known that the uterine environment is a factor independent of genes. As an example, a recent study shows that infants tend like foods that their mothers ate during pregnancy. That is a clear case of a preference formed in utero without specific genes.
http://www.npr.org/2011/08/08/139033757/…

There is evidence for biological determination of sexual preference.
http://endo.endojournals.org/content/145…

I think when they say born with they mean more of preference wise... Like how some colors just look tacky to you or how some people don't like wearing uncomfortable clothing.