Very simple Jason_Els,
If it was a dominant gene there would be more gay than straight babies born and the species would be doomed to die out due to the lack of offspring being born.
Not quite that simple Dustydo,
It's commonly misunderstood that in genes, "dominant" means stronger, with "recessive" meaning weaker.
Genetically, "dominant" does not mean stronger. It simply means that if you possess that gene, it will be expressed, or "show". Recessive genes can be present, but hidden.
If there were such a thing as the "gay gene", and it was recessive, a person could possess that gene, and not express it. It could possibly be passed on and expressed in future generations.
If it were a dominant gene, then it gets even more confusing because since it is not phonetically (visually) expressed, even if they possessed the gene, a person could hide it out of shame or fear.
However, Back On Topic, (lol) I used to believe that it existed, now I would vote "Fiction".