Histones and chromatin structure in Tetrahymena macro- and micronuclei

can be used to study relat ionships between histones (and their modifications), chromatin structure, and genetic activity. In this paper we compare histones and chromatin structure in macro- and micro-nuc le i- two structural ly and functional ly distinct nuclei which share a common cytoplasm. A sub-sequent paper (Mathis and Gorovsky, this vol-ume) compares nuclease digestion propert ies of genes coding for r ibosomal RNA (rRNA) with those of the bulk chromatin of the macronucleus. Properties of Macro- and Micronuclei Vegetative cells of most species of Tetrahymena contain two types of nuclei. When cells of different mat ing types from the same species (syngen) are mixed under appropr iate conditions (Bruns an