The objective is to test certain conjectures on the mechanism of regulation of histone genes in the sea urchin. The sequence organization of histone genes in the sea urchin will be analyzed using a combination of electron microscope techniques and restriction enzyme studies. A basic repeat of the 5 principal histone genes has already been identified but some heterogeneity of this repeat is known to exist. This study will determine the organization of genes in several contiguous repeats both in total DNA and in DNA cloned in chimeric plasmids. It will also determine whether alternate forms of the repeat exist, using mRNA isolated from several developmental stages as a probe. Sea urchin RNA polymerase II will be purified and bound to repeats of histone genes. Specific binding sites (promotors) on the repeats will be isolated, characterized and sequenced. The primary transcript of the histone genes will be isolated. The order of specific sequences on the primary transcript will be determined by hybridization of the RNA to chimeric plasmid DNA.