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.
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Abbreviations
- ITS:
-
Interstitial telomeric sites
- FISH:
-
Fluorescence in situ hybridization
- FN:
-
Fundamental number
- NORs:
-
Nucleolar organizer regions
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Acknowledgments
The authors are grateful to Alexandre Uarth Christoff, Juliana Marge Pagnozzi, Pedro Luis Bernardo da Rocha, Raquel Pena de Oliveira and Valéria Fagundes for collecting the specimens, and to Tien Hsi Chu and Miriam Romeo for technical assistance. We are very grateful to Katia Cristina Machado Pellegrino for the valuable comments and suggestions on the manuscript. Grants for this study were provided by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP). The specimens were collected under permission of Instituto Brasileiro do Meio Ambiente e Recursos Naturais Renováveis (IBAMA no 02001.003451/93-13 AC and no 02001.002750/96-93).
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Amaro-Ghilardi, R.C., Silva, M.J.d.J., Rodrigues, M.T. et al. Chromosomal studies in four species of genus Chaunus (Bufonidae, Anura): localization of telomeric and ribosomal sequences after fluorescence in situ hybridization (FISH). Genetica 134, 159–168 (2008). https://doi.org/10.1007/s10709-007-9218-6
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DOI: https://doi.org/10.1007/s10709-007-9218-6