Nucleolus organizer regions and nucleoli.
D000818:Animals; D002466:Cell Nucleolus / Q000502:physiology / Q000648:ultrastructure*; D006801:Humans; D008214:Lymphocytes / Q000648:ultrastructure; D008677:Metaphase; D008854:Microscopy, Electron; D012313:RNA / Q000032:analysis; D013194:Staining and Labeling; D014158:Transcription, Genetic
D012313:RNA