The long range goal of our research is to understand how organisms develop into organized patterns. In particular, we are interested in how spatial and temporal differences in gene activities are established, altered, propagated, and expressed on the cell surface. For all our investigations we use fly, Drosophila melanogaster, because of the powerful molecular and genetic techniques available. First, we will identify what makes the genome become transcriptionally active. For this we will use inhibitors that block specific cellular events. Second, we will examine how complex patterns of gene expression develop. Our working hypothesis is that early in development all patterning genes are switched on everywhere but subsequently become repressed in particular regions. Third, we will examine the role of three cytoplasmic components in regulating expression of patterning genes: the ability to translate proteins, the role of microtubules, and the necessity of long range interactions within the egg cell. The fourth area of investigation addresses the role of cell surface differences in pattern formation. We plan to identify cell surface molecules responsible for cell recognition and test what role they play in morphogenesis. These studies should provide insight into the regulation of gene activities early in animal development and into the cytoplasmic and cell surface manifestations of different determined states.