title: Altered genetic code in Paramecium mitochondria: possible evolutionary trends.
abstract: The sequence and presumptive structure of a tRNA trp gene from Paramecium tetraaurelia are given. The gene is located 1,500 bp downstream from the 13S rRNA gene, in about the middle of the genome. Paramecium tRNA trp has a completely normal TpsiC loop and stem, however its anticodon (UCA) constitutes an alteration in the "universal" genetic code, similar to those seen in fungal and mammalian mitochondria. Most features of Paramecium tRNA trp resemble other mitochondrial counterparts; however, its sequence is more homologous to the "unaltered" tRNA trp (anticodon CCA) from E. coli. Paramecium mitochondria may resemble a primitive stage of organelle evolution.
mesh_terms: D001483:Base Sequence; D005075:Biological Evolution; D004247:DNA; D008928:Mitochondria / Q000648:ultrastructure*; D010247:Paramecium / Q000235:genetics*; D012343:RNA, Transfer
chemical_list: D004247:DNA; D012343:RNA, Transfer