(Crosspost from GeneticFuture.org.)

The results of a study published this week suggest an undeniable connection between genetics and sexual behavior -- at least with fruit flies.

A single gene appears to be responsible for whether a fruit fly will court male or females, regardless of its own gender.

[ From Medical News Today ]
A male fly's sexual courtship of a female fly is a complicated business of tapping, singing, wing vibration, and licking, but a single gene is all that is needed to produce this complex behavior, according to new research published in this week's issue of the journal Cell.

Dickson and Demir created male-spliced versions of fruitless in female flies and female-spliced versions in male flies. Males with the female version of fruitless "barely court at all" when paired with virgin female flies in an observation chamber, according to the researchers.

Males with the female fruitless splice form were also more likely to court other males than flies with the male form, suggesting that male-specific fruitless splicing "not only promotes male-female courtship, it also inhibits male-male courtship," the researchers say.
Dickson and Demir refer to fruitless as a behavioral "switch gene" that is both necessary and sufficient to produce a particular behavior. Switch genes that trigger the development of a particular anatomical feature like wing structure have been studied extensively, but there are very few studies of switch genes that control a complex behavior, the researchers note.

None of the news is bold enough to suggest a human connection, i.e. a genetic basis for homosexuality, but it's hard to overlook the fact that fruit flies share 60% of their genes with humans. Furthermore, fruit flies have been a hot subject for study since 2000, when it was discovered that they employ eerily similar genetic mechanisms as humans for morphological development into adults. [Didn't your heart race during that brief excitement in 2000 when virtually all 13,601 genes belonging to the fruit fly genome were decoded?]