I will take into consideration genes for you and still prove your contradiction.
In genetics, a particular condition can be "in our genes" (or "genetic") without there being a specific gene (or location on the genome) for that particular trait or condition.
So you are telling me that something that has no specific genes can still be in our genes? If there's no sexual orientation gene, heterosexuality is therefore not in our genes. It's physically impossible. No, I'm not a genetic expert but you clearly have zero knowledge on how genes actually work. What you fail to understand is that heterosexuality is a form of sexual orientation so if that gene doesn't exist, heterosexuality is not in our genes. For you to say otherwise destroys all credibility you have on the subject.
Are you happy now? Does this suffice as taking genetics into consideration because your statements are still contradictory. Learn what sexual orientation is and that heterosexuality is part of sexual orientation.