The Formation of Dumpy Vortices in Mosaics of Drosophila Melanogaster.

NTERMEDIATE patterns in development have been termed “prepatterns” I by STERN (1954a,b). STERN hypothesized that the determinations of some cells depend on the particular environments of their positions in intermediate patterns and that some genes may act to alter these patterns. A genetically based change in the prepattern could thus indirectly affect the final pattern of differentiated cells. There is good evidence for dependent differentiation in Drosophila metamorphosis. Regulative morphogenic fields within imaginal discs have been shown (HADORN 1953; for review in English see URSPRUNG 1963). Earlier evidence that imaginal disc development is not strictly determinative was the fact that cell lineage is not constant, as shown by the overlapping shapes of the mosaic patches themselves (STERN 1940). Induction of ectodermal structures by mesodermal tissue has been shown in other insects (BOCK 1939). In Drosophila it is possible to produce somatic mosaic such that areas of one genotype appear on a background of a contrasting genotype. X-irradiation during development can cause mitotic crossing over so that the genotype of a proliferating cell can be changed from heterozygosity to homozygosity for a group of linked alleles ( BECKER 1956a, 195 7). Morphogenic mutants linked to marker genes can be used to study the developmental interactions of tissues of different genetic compositions. Marked mosaics of a number of morphogenic mutants have been studied, including mosaics of some homoeotic mutants: the bithorax series (LEWIS 1963) , engrailed (TOKUNAGA 1961), and extra sex comb (C. TOKUNAGA, in preparation). All pattern forming genes studied in this way have proven to be autonomous, each cell differentiating according to its own genotype. These genes apparently effect differential responses to an unchanging prepattern. In the present study, mosaics of a pattern determining mutant dumpy ( d p ) , show a different aspect of pattern formation. Before the mosaics would be meaningful a careful description of the mutant phenotype was necessary.