The long-term goal of the proposed research is to understand the control of spatially coordinated cell differentiation. The short- term goal is to establish the common and unique aspects of development of two different body segments of Drosophila melanogaster by comparing the status of positional information and determination in the imaginal discs of the oculoantennary (OA) and mesothoracic (MS) segments and to catalog the regions of the OA transformed into MS structures by a variety of mutant loci including alleles of the homoeotic gene Antennapedia. Homologies of positional information in OA and MS will be ascertained by determining 1) the new identity of individual OA structures when they are transformed into MS structures by homoeotic mutants and 2) the regulative interactions which take place between a variety of small non-regenerating fragments of OA and MS imaginal discs when they are grafted together and cultured in vivo; grafted fragments with homologous positional information fail to regenerate. The status of determination of cells in the OA and MS will be established by testing the regulative potential of dorsal and ventral portions of these segments in grafts between small non-regenerating fragments of dorsal and ventral primordia. The ability of dorsal primordia to regenerate ventral primordia (and vice verse) is evidence for a common state of determination of these dorsal and ventral primordia. A second short-term goal is to catalogue the positional specificity of the effects of different alleles of the Antennapedia locus in order to understand how this gene might serve different functions in different portions of the segment. An explanation of the cellular, genetic and molecular bases of the control of cell determination, proliferation and differentiation has clear implications for the understanding of normal and abnormal human development and may shed light on some aspects of the establishment and maintenance of the cancerous state.