The goal of these projects is to determine the mechanisms by which isotypes of multi-gene families are differentially regulated in embryogenesis and during differentiation. Furthermore, these studies are aimed at determining the structural and functional relationships of various messenger RNAs. These projects directly address fundamental principles of animal cell molecular biology which are grossly disturbed in abnormal aspects of development, cell growth and malignancy. Our projects will examine the organization and expression of histone genes in sea urchins. We will study the physiologic mechanisms controlling histone gene expression that is differentially regulated in embryonic development. We will introduce normal and modified histone mRNAs into zygotes in order to explore questions about their normal regulation. We will examine the evolutionary and structural aspects of several sea urchin transposable elements and establish a functional assay for eukaryotic transposition.