"Both male and female flies have the same genetic material as well as the neural circuitry required for the mating ritual, but different parts of the genes are turned on in the two sexes. But no one dreamed that simply activating the normally dormant male portion of the gene in a female fly could cause a genetic female to display the whole elaborate panoply of male fruit fly foreplay."
The important point here is that all fruit flies, male and female, carry the genes which, when activated, produce either male or female orientation and mating behavior. This includes the "master gene" which produces a different sex specific protein based on other male v female signals that direct mRNA splicing to produce either the male or female version of this protein. Then this one protein controls the activation of one of the two sets of genes that alternately produce either male or female orientation and behavior.
This study parallels what I was saying in my previous post Genetic Basis for Sexual Orientation
. We all carry the sets of genes which would lead us to be attracted to either males or females. It is the signal provided by the presence or absence of the Y chromosome after fertilization which usually selects the set associated with the opposite sex. Yet our experience shows that at times this signaling can go awry and we experience others who are attracted to the same sex, to both sexes or neither.
While human behavior is more complex than that in these flies, we cannot deny that the sexual arousal response that is programmed in the limbic system by our genes is by its primitive nature quite compelling. More importantly, it leads to the bonds of love and affection that cannot form when this genetic predisposition is absent.
There is no one gene for homosexuality. We all have the sets of genes that, when selected like in these flies, would result in our being attracted to and reacting to either males or females, our biological sex not withstanding. Sexual orientation is an inborn characteristic based on these genetic factors that cannot be changed. The sooner we all understand and accept this the better.