From The New York Times:
When the genetically altered fruit fly was released into the observation chamber, it did what these breeders par excellence tend to do. It pursued a waiting virgin female. It gently tapped the girl with its leg, played her a song (using wings as instruments) and, only then, dared to lick her – all part of standard fruit fly seduction. The observing scientist looked with disbelief at the show, for the suitor in this case was not a male, but a female that researchers had artificially endowed with a single male-type gene. That one gene, the researchers are announcing today in the journal Cell, is apparently by itself enough to create patterns of sexual behavior – a kind of master sexual gene that normally exists in two distinct male and female variants.
In a series of experiments, the researchers found that females given the male variant of the gene acted exactly like males in courtship, madly pursuing other females. Males that were artificially given the female version of the gene became more passive and turned their sexual attention to other males.
“We have shown that a single gene in the fruit fly is sufficient to determine all aspects of the flies’ sexual orientation and behavior,” said the paper’s lead author, Dr. Barry Dickson, senior scientist at the Institute of Molecular Biotechnology at the Austrian Academy of Sciences in Vienna. “It’s very surprising. “What it tells us is that instinctive behaviors can be specified by genetic programs, just like the morphologic development of an organ or a nose.”
More here.