Molecular cytogenetics in planarians. I. Fluorescence in situ hybridization (FISH) of ribosomal DNA to mitotic chromosomes of Dugesia sicula Lepori (Turbellaria: Tricladida)

Abstract

SUMMARY -The nucleolus organizing regions (NORs) were detected on mitotic chromosomes of the freshwater planarian Dugesia sicula Lepori, by the in situ fluorescence technique (FISH). The results show that ribosomal DNA ( rDNA) sequences are located on medium-sized chromosomes, at telomeric positions. The application of the in situ hybridization method, which enables the molecular arrangement of specific DNAs to be visualized on the chromosomes, improves the karyotypic characterization in planarians and is of interest in a cytogenetic and cytotaxonomic perspective.