A sex-specific switch

摘要

Those who are intimate with the fruitfly Drosophila melanogaster will recognize this fine specimen as a male. Most notably, the last two of its abdominal segments are pigmented. The equivalent segments in the posterior abdomen of females lack pigment, and sexual dimorphism of this and many other forms is responsible for all sorts of male-female behavioural differences in all sorts of organisms - vertebrate and invertebrate. Thomas Williams and colleagues have dissected this instance of fruitfly sexual dimorphism in molecular detail to reveal the genetic switch concerned. The pigmentation is regulated by the tandem duplicate bab genes, whose protein products repress the enzyme system that produces pigment.