Development in Genetic Mosaics of Aristapedia, a Homoeotic Mutant of DROSOPHILA MELANOGASTER

Development of the homoeotic mutation, aristapedia (ss(a)), was investigated by means of genetic mosaics. The wild-type alleles of aristapedia and the bristle markers yellow, singed, and forked were removed from cells at different times in development by X-ray induced somatic crossing-over. The phenotype of the resulting clones was examined in order to ascertain whether it was leg or antenna. The y sn f; ss(a) clones showed a leg phenotype if induced before the mid-third instar, but showed an antennal phenotype if induced after this time. Late non-expression of ss(a) may be due either to an influence of surrounding ss(+) tissues on the small ss(a) clones, or to a persistence of the effect of ss(+) for one or two cell generations after it is removed from a cell line.