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Free Content Analyses of the Structure of NORs in Two Species of South American Sorubiminae Fishes (Siluriformes) by Means of Several Cytogenetic Techniques

Several cytogenetic techniques (AgNOR, C- G- and RE bandings, DAPI, CMA3 and FISH) were applied in order to analyze the structure and variability of NORs in the fish species Steindachneridion melanodermatum and S. scripta. Ag-NORs were observed on the short arm of the first acrocentric chromosome pair, coincidentally with a strong C-positive band on a large secondary constriction. In addition, NORs showed bright fluorescent signals when stained with CMA3 and treated for FISH with rDNA 18S. However, they showed negative coloration after G- and restriction enzyme banding and DAPI staining. The results evidence a substantial size polymorphism in these regions. The NOR bearing chromosomes in both species may be considered homologues because they maintain conserved characteristics, such as being interspersed with a GC-rich heterochromatin and possessing target sequences for Alu I, BamHI and EcoRI.

Keywords: NEOTROPICAL FISHES; NOR POLYMORPHISM; STEINDACHNERIDION

Document Type: Research Article

Publication date: 2008

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  • Folia biologica is an international quarterly journal that publishes papers on the broad field of experimental zoology, nuclear and chromosome research, and also ultrastructural studies. All papers are subject to peer reviews. Indexed in: ISI Master Journal List, Current Contents, Polish Scientific Journals Contents. I.F. 0.667
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