title: The organization of ribosomal genes in diploid and tetraploid species of the genus Odontophrynus (Amphibia, Anura).
abstract: The organization of the repeat unit of the ribosomal genes was determined in populations of Odontophrynus americanus 2n, 4n, O. occidentalis 2n and O. barrioi 2n (Amphibia, Anura) from South America. HindIII, EcoRI and BamHI restriction patterns of rDNA from single individuals were probed with two rDNA clones from Xenopus laevis. Variations in length and sequence were found among different species, populations and specimens. A general pattern could be established from the most frequent type of repeat observed in each case, so that diploid populations could be distinguished from tetraploid ones. The molecular evolution of variant repeats is discussed. It is suggested that the reduced size of the non-transcribed spacers in the tetraploids from São Paulo could play a role in the control of rDNA transcription. Distinct restriction maps were tentatively correlated to the varying localization of active rDNA clusters on metaphase chromosomes of corresponding populations.
authors.affiliation: Laboratoire de Génétique Moléculaire, Institut Jacques Monod, Université Paris VII, France.
authors.forename: J
authors.initials: J
authors.lastname: Cortadas
authors.forename: I R
authors.initials: IR
authors.lastname: Ruiz
mesh_terms: D000818:Animals; D001001:Anura / Q000235:genetics*; D001118:Argentina; D001938:Brazil; D004262:DNA Restriction Enzymes; D004275:DNA, Ribosomal / Q000235:genetics*; D005260:Female; D005786:Gene Expression Regulation; D005796:Genes; D008297:Male; D009693:Nucleic Acid Hybridization; D011123:Polyploidy; D012091:Repetitive Sequences, Nucleic Acid; D013045:Species Specificity
chemical_list: D004275:DNA, Ribosomal; D004262:DNA Restriction Enzymes