The organization of the chromatin-containing ribosomal genes of Tetrahymena will be studied. Non-specific nucleases (DNAse I, DNAse II, Exonuclease III) will be used as probes. The organization of non-transcribed spacers will be compared with that of transcribed spacers. The histones and chromatin structure of Tetrahymena macro- and micronuclei will be studied. Methods will be developed for reconstituting nucleosomes using Tetrahymena histones. The sequence of Tetrahymena H4 (and possibly H3 and HX) will be determined.