title: Chromosomal studies in four species of genus Chaunus (Bufonidae, Anura): localization of telomeric and ribosomal sequences after fluorescence in situ hybridization (FISH).
abstract: Fluorescence in situ hybridization (FISH) using telomeric and ribosomal sequences was performed in four species of toad genus Chaunus: C. ictericus, C. jimi, C. rubescens and C. schneideri. Analyses based on conventional, C-banding and Ag-NOR staining were also carried out. The four species present a 2n = 22 karyotype, composed by metacentric and submetacentric chromosomes, which were indistinguishable either after conventional staining or banding techniques. Constitutive heterochromatin was predominantly located at pericentromeric regions, and telomeric sequences (TTAGGG)(n) were restricted to the end of all chromosomes. Silver staining revealed Ag-NORs located at the short arm of pair 7, and heteromorphism in size of NOR signals was also observed. By contrast, FISH with ribosomal probes clearly demonstrated absence of any heteromorphism in size of rDNA sequences, suggesting that the difference observed after Ag-staining should be attributed to differences in chromosomal condensation and/or gene activity rather than to the number of ribosomal cistrons.
authors.affiliation: Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, Rua do Matão, 277, São Paulo, SP, CEP 05508-900, Brazil. amarorc@usp.br
authors.forename: Renata Cecília
authors.initials: RC
authors.lastname: Amaro-Ghilardi
authors.forename: Maria José de Jesus
authors.initials: MJ
authors.lastname: Silva
authors.forename: Miguel Trefaut
authors.initials: MT
authors.lastname: Rodrigues
authors.forename: Yatiyo
authors.initials: Y
authors.lastname: Yonenaga-Yassuda
mesh_terms: D000818:Animals; D002025:Bufonidae / Q000097:blood / Q000145:classification / Q000235:genetics*; D002871:Chromosome Banding; D002875:Chromosomes; D020732:Cytogenetic Analysis; D015342:DNA Probes; D004275:DNA, Ribosomal / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D009697:Nucleolus Organizer Region / Q000235:genetics* / Q000648:ultrastructure; D015347:RNA Probes; D016622:Silver Staining; D016615:Telomere / Q000235:genetics* / Q000648:ultrastructure
chemical_list: D015342:DNA Probes; D004275:DNA, Ribosomal; D015347:RNA Probes