GENETIC CONTROL OF PATTERN DETERMINATION IN DROSOPHILA. THE ACTION OF HAIRY-WING

Abstract

A developmental analysis of the differences in differentiation in tissues of the Hairy-wing (Hw) homozygous, heterozygous and Hw/sup +/ homozygous genotypes was performed utilizing genetic mosaics produced by x-ray-induced crossing over in heterozygous larvae. The mosaics and controls were characterized by a series of measurements and counts in the dorsocentral region. Interactions were observed between the three different genotypes in mosaics. Hw/ Hw tissue acts semiautonomously in mosaics, having an expression, in the dorsocentral region, 0.64 that of the homozygote controls. Hw/sup +//Hw/sup +/ tis sue acts nonautonomously and will occasionally produce extra macrochaetae in the presence of adjacent Hw/Hw tissue. X irradiation causes Hw heterozygotes to express themselves in a homozygous-like fashion. Making Hw/Hw and Hw/sup +//Hw/ sup +/ coisogenic for their second and third chromosomes, while it effects the linear dimensions, does not alter the numbers of chaetae. The evidence suggests that Hw alters both the prepattern and the competence of the differentiating hypodermal cells. (auth)