On the one hand, this is a strange tale of mutant, bisexual, necrophiliac flies, and you’ve got to love it for the titillating nature of the experiments. But on the other, much more interesting hand, it’s a story about drilling down deeply into the causes of a complex behavior, and tracing it to a single gene product — and it also reveals much about the way the chemicals sloshing about in the brain can modulate responses to stimuli. Work by Grosjean and others on a simple Drosophila mutant, genderblind, which causes flies to be indiscriminate about gender in their courtship, opens up a window into how sexual responses are shaped and specified.
Think about human sexual responses. Some of us, when we see an attractive woman, are at least mildly aroused; others are have their sexual interest picqued when they see an attractive man; still others might feel sexual urges when they see a shoe, or a plush animal, or a pot of baked beans. No matter what the stimulus, these are all biological responses, with something in the environment matching some trigger in our brains and initiating a cascade of neural, neurochemical, and hormonal activity that leads to sexual behaviors. The question we want to address is what every step in the biology is doing; unfortunately, human behaviors are both too complex and not amenable to ethical experimentation, so we turn instead to simpler organisms that allow us to find simpler causes and carry out thorough experiments to probe the behavior.
