The general goal of the research outlined in this proposal is to gain some further insights into the processes involved in gene expression and the utilization of genetic information in eukaryotes. The proposed work focuses on two different areas of research. The first area is the structure and function of higher order chromosomal domains. The studies described in the proposal include 1) the analysis of the processes involved in the decondensation/condensation of these higher order domains during gene activation and de-activation, and 2) molecular and genetic studies aimed at characterizing the structure and function of the (putative) boundaries or anchor points of these higher order chromosomal domains. The second area is the molecular and biochemical characterization of a complex regulatory locus, Sexlethal, which plays a central role in the development of sexual dimorphism in Drosophila. The studies described in the proposal include 1) a detailed analysis of the sequence organization and coding properties of the Sxl gene+ and 2) the identification and characterization of the (putative) protein products encoded by this gene.