title: Karyotypic characterization and genomic organization of the 5S rDNA in Polypterus senegalus (Osteichthyes, Polypteridae).
abstract: Polypteridae (Cladistia) is a family of archaic fishes, confined to African freshwaters. On account of their primitiveness in anatomical and morphological characters and mosaic relationships among lower Osteichthyans fishes, they constitute an important subject for the study of evolution in vertebrates. Very little is known about the karyological structure of these species. In this article, a cytogenetic analysis on twenty specimens of Polypterus senegalus (Cuvier, 1829) was performed using both classical and molecular techniques. Karyotype (2n=36; FN=72), chromosome location of telomeric sequences (TTAGGG)(n), (GATA)(7) repeats and ribosomal 5S and 18S rRNA genes were examined by using Ag-NOR, classical C-banding, CMA(3) staining and FISH. Staining with Ag-NOR showed the presence of two GC rich NORs on the p arm of the chromosome pair no. 1. CMA(3) marked all centromerical and some (no. 1 and no. 14) telomeric regions. FISH with 5S rDNA marked the subtelomeric region of the q arm of the chromosome pair no. 14. FISH with 18S rDNA marked the telomeric region of the p arm of the chromosome pair no. 1, previously marked by Ag-NOR. (GATA)(7) repeats marked the subtelomeric regions of all chromosome pairs, with the exclusion of the no. 1, 3 and 14. Hybridization with telomeric probes (TTAGGG)(n) showed bright signals at the end of all chromosomes. After cloning, the 5SrDNA alignment revealed an organization of sequences made up of two different classes of tandem arrays (5S type I and 5S type II) of different lengths.
authors.affiliation: Dipartimento di Scienze della Vita, Seconda Università degli Studi di Napoli, Via Vivaldi 43, 81100 Caserta, Italy. maria.morescalchi@unina2.it
authors.forename: Maria Alessandra
authors.initials: MA
authors.lastname: Morescalchi
authors.forename: Innocenza
authors.initials: I
authors.lastname: Liguori
authors.forename: Lucia
authors.initials: L
authors.lastname: Rocco
authors.forename: Aristea
authors.initials: A
authors.lastname: Archimandritis
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Stingo
mesh_terms: D000818:Animals; D001399:Azure Stains; D001483:Base Sequence; D002871:Chromosome Banding; D002875:Chromosomes / Q000235:genetics; D016384:Consensus Sequence / Q000235:genetics; D004275:DNA, Ribosomal / Q000235:genetics*; D005260:Female; D049751:Genome, Helminth / Q000235:genetics*; D006039:Gnathostoma / Q000166:cytology / Q000235:genetics*; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D008677:Metaphase / Q000235:genetics; D018895:Microsatellite Repeats; D008969:Molecular Sequence Data; D012341:RNA, Ribosomal, 5S / Q000235:genetics*; D017422:Sequence Analysis, DNA
chemical_list: D001399:Azure Stains; D004275:DNA, Ribosomal; D012341:RNA, Ribosomal, 5S