Mutant flies can't get no satisfaction.

The genetics of human sexual behavior is a minefield, as the ongoing debate over the existence of a gay gene aptly shows. The sexual habits of insects, and the genes that drive them, are a bit less prone to provoke newspaper editorials. Still, scientists have identified gene mutations that turn a male fruit fly's fancy to others of his sex and that disrupt his courtship ritual (SN: 12/4/96, p. 373). They've now found a gene involved in both male and female sexual behavior.

The gene is named dissatisfaction because female flies with mutations in it vigorously dismiss male advances. If fertilized despite their resistance, these females fail to lay eggs because they can't control their uterine muscles. As for males with the mutant gene, they mistakenly try to mate with males as well as females and also have neuromuscular defects that make it difficult for them to copulate.

In the December 1998 NEURON, Michael McKeown of the Salk Institute for Biological Studies in San Diego and his colleagues identify dissatisfaction as a gene encoding a protein that regulates other genes. The gene is active in as few as 25 to 50 brain cells. The researchers believe that dissatisfaction is part of a set of genes regulating sexual behavior independently of the two genes already known to influence male fruit fly courtship, fruitless and doublesex.

"We're in the process of looking for dissatisfaction-like genes in vertebrates," notes McKeown. The researcher argues that although people are obviously much more complex than flies, the notion that genes influence human sexual behavior has to be taken seriously.