REPEATED DNA AND HETEROCHROMATIN STRUCTURE IN RUMEX-ACETOSA

Seven clones, six of which represent moderate to highly repeated seque nces, were isolated from a plasmid clone bank of EcoRI-digested Rumex acetosa DNA. All sequences revealed a dispersed nature when chromosome s were probed by in situ hybridization. Studies of RNA transcription b y these sequences indicate that one, pRa141, may be actively transcrib ed. The implications of these results on the current understanding of the nature of the chromatin in the R. acetosa Y chromosome are discuss ed. Preliminary evidence is produced for a facultative heterochromatic sex system in plants.