Genetic analysis of transdetermination in Drosophila. II. Transdetermination to wing of leg discs from a mutant which lacks wing discs.

Drosophila melanogaster larvae homozygous for lethal mutations at the L6 locus have no wing discs. However, like wild-type leg discs, leg discs from such mutant larvae can transdetermine to wing. Apparently such a transdetermination event bypasses the block to wing disc development caused by mutations at this locus. In order to evaluate the significance of this observation we have examined the cell autonomy of the mutant phenotype and the capacity of mutant larvae to support the growth of normal wing discs. The mutation appears not to be expressed cell autonomously, yet mutant larvae can support the growth of normal wing discs. One way of resolving these paradoxical results is to hypothesize that the normal product of the L6 gene is essential only for an initial step of wing disc development. According to this hypothesis, the fact that mutant leg discs can transdetermine to wing implies that transdetermination does not proceed by recapitulating that step of normal wing disc development.