CONTRIBUTION OF THE GENE EXTRAMACROCHAETAE TO THE PRECISE POSITIONINGOF BRISTLES IN DROSOPHILA

We examine the effect of mutations in the extramacrochaetae (emc) gene on the positioning of macrochaetes on the notum of Drosophila. We sho w that, in emc mutants, most of the precursor cells appear earlier tha n in wild-type individuals, consistent with an antagonizing effect of emc on the action of the proneural genes achaete and scute. We also sh ow that reducing emc function affects the position of three bristles a nd/or of their precursors, but has no marked effect on the positioning of the other bristles.