In part, this is because finding behavioral switch genes can be a difficult task. The key, says Dickson, is demonstrating that a specific gene is sufficient to produce a particular behavior.
"This means showing that gene X is sufficient to create the potential for behavior Y in an otherwise normal animal. It is the 'otherwise normal' part that is tricky," he says.
"Putting gene X into another species and expecting to see a behavior is unrealistic--a 'flight' gene from Drosophila, if it existed, is not going to make a mouse fly," Dickson explains, noting that only members of the same species might be expected to share the same set of "normal" behaviors.
"So you need to put gene X in a normal animal of the same species that doesn't normally do Y. This is really only possible with sex-specific behaviors" like courtship, he says.
Dickson also says there is "something of a debate going on between the view that single genes can have profound effects on behavior, versus the more holistic view that behavior is so complex that we can never learn anything meaningful about a behavior by studying the action of a single gene."
Still, studies show that a single gene can trigger the development of complex anatomical structures like eyes or limbs, by influencing sometimes hundreds of other genes, Dickson notes.
"I don't see any good reason why innate behaviors, which are a consequence of how the nervous system is built, should be any different. Indeed, I think that is what our work shows," he says.
In a second Cell paper, Dickson and colleagues demonstrate that nerve cells expressing the fruitless gene are linked in a circuit in both males and females. The finding suggests that the "essential difference in sexual behavior between males and females lies