Mosaics Involving Aristapedia, a Homeotic Mutant of Drosophila Melanogaster.

A homeotic mutant alters an appendage of a segmental series from its typical form to that of some other member of the series. One mutant usually classified as homeotic is aristapedia (BALKASCHINA 1929), which transforms the arista of the antenna into a tarsus-like structure (Figure 1). Most mutants that have been studied by means of genetic mosaics can be considered late acting in that they appear to alter the competence of cells to respond to preexisting inducing fields or "prepatterns" (STERN 1954; TOKUNAGA 1961 ) . Because of the drastic nature of the transformation, it has been suggested (HANNAH-ALAVA 1958) that homeotic mutants alter prepatterns. The study reported here presents evidence that the homeotic mutant, aristapedia, alters the response of antennal cells rather than altering the prepattern.