title: Extrachromosomal ribosomal RNA genes in Tetrahymena: structure and evolution.
mesh_terms: D000818:Animals; D005075:Biological Evolution; D004247:DNA / Q000378:metabolism; D005796:Genes; D009693:Nucleic Acid Hybridization; D012335:RNA, Ribosomal / Q000096:biosynthesis*; D013045:Species Specificity; D013768:Tetrahymena / Q000378:metabolism*
chemical_list: D012335:RNA, Ribosomal; D004247:DNA