Genomic transcriptional activity and the structure of chromatin

Abstract
Nucleic acid hybridization showed that micrococcal nuclease-derived chromatin subunits from the cells of Xenopus laevis contain fragments of ribosomal 28S, 18S and 5S RNAs within the population of 200 base-pair pieces of DNA. Subunits from cultured embryonic cells actively transcribing ribosomal RNA contain only 70-74% of the cistrons present in undigested wild-type DNA, while subunits from adult erythrocytes not active in RNA transcription contain close to 90% of the ribosomal cistrons in native chromatin.