[Characteristics of the scutellar bristle pattern in Drosophila melanogaster mutants al, h and al; h].

The object of this study was the distribution of macrochaetae and microchaetae on the scutellum of Drosophila melanogaster in wild-type individuals and in three mutant genotypes: h/h, al/al and al; h/al; h. The mutation h (hairy) causes the appearance on the scutellum of extra microchaetae with a definite distribution pattern. The mutation al (aristaless) changes the size and the shape of scutellum and causes the shift of the posterior scutellar bristles. It is shown by the study of double homozygotes al; h/al; h, that this bristle can be shifted into the region occupied by one of microchaetae. The results obtained are considered in the light of the prepattern hypothesis. An assumption is made about the possible three-component constitution of the system of pattern formation.