title: The 18S rRNA from Odontophrynus americanus 2n and 4n (Amphibia, Anura) reveals unusual extra sequences in the variable region V2.
abstract: The nucleotide sequence of the rDNA 18S region isolated from diploid and tetraploid species of the amphibian Odontophrynus americanus was determined and used to predict the secondary structure of the corresponding 18S rRNA molecules. Comparison of the primary and secondary structures for the 2n and 4n species confirmed that these species are very closely related. Only three nucleotide substitutions were observed, accounting for 99% identity between the 18S sequences, whereas several changes were detected by comparison with the Xenopus laevis 18S sequence (96% identity). Most changes were located in highly variable regions of the molecule. A noticeable feature of the Odontophrynus 18S rRNA was the presence of unusual extra sequences in the V2 region, between helices 9 and 11. These extra sequences do not fit the model for secondary structure predicted for vertebrate 18S rRNA.
authors.affiliation: Genetics Laboratory, Butantan Institute, São Paulo, Brazil.
authors.forename: Lúcia E
authors.initials: LE
authors.lastname: Alvares
authors.forename: Jan
authors.initials: J
authors.lastname: Wuyts
authors.forename: Yves
authors.initials: Y
authors.lastname: Van de Peer
authors.forename: Eduardo P
authors.initials: EP
authors.lastname: Silva
authors.forename: Luiz L
authors.initials: LL
authors.lastname: Coutinho
authors.forename: Olivier
authors.initials: O
authors.lastname: Brison
authors.forename: Itamar R G
authors.initials: IR
authors.lastname: Ruiz
mesh_terms: D000818:Animals; D001001:Anura / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular; D004275:DNA, Ribosomal / Q000235:genetics*; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D011003:Ploidies; D012337:RNA, Ribosomal, 18S / Q000737:chemistry / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid; D014982:Xenopus laevis
chemical_list: D004275:DNA, Ribosomal; D012337:RNA, Ribosomal, 18S