Gene change alters fruit fly sex orientation

Altering a single gene in a fruit fly can turn its sexual orientation around, causing male flies to lose interest in females, and females to display male mating rituals to other females, according to a study published in the journal Cell on Friday.
The research by Barry J. Dickson and Ebru Demir of the Institute of Molecular Biotechnology of the Austrian Academy of Sciences into the workings of a “switch gene” touched on the scientific debate about whether genes or environment determine human sexual orientation. Male courtship in Drosophila is an elaborate ritual and largely a fixed-action pattern easily identified by the researchers.
The male taps the female with his forelegs, sings a specific courtship song by extending and vibrating a wing, licks her genitalia, and then curls his abdomen for copulation.
Through gene splicing, they were able to swap the orientation of male and female fruit flies they studied in an observation chamber.
“Forcing female splicing in the male results in a loss of male courtship behavior and orientation,” the study said. “More dramatically, females ... spliced in the male mode behave as if they were males: they court other females.
“A complex innate behavior is thus specified by the action of a single gene, demonstrating that behavioral switch genes do indeed exist.” Female flies with the male version of the gene also made amorous advances toward male flies expressing female pheromones, while altered male flies were more likely to court other males.
“We have been able to reverse the sex roles during Drosophila courtship,” the scientists said.
So-called “switch genes” that trigger development of an anatomical feature such as wing structure had been extensively studied, but there were few studies of switch genes that control a complex behavior, the researchers said.
The researchers said they had already begun work with other scientists to test for switch genes that might be linked to other behavioral patterns like aggression.