Major and 5S ribosomal sequences of the largemouth bass Micropterus salmoides (Perciformes, Centrarchidae) are localized in GC-Rich regions of the genome

Major and 5S ribosomal genes have been localized in the chromosomes of Micr opterus salmoides. By C-banding, Ag-staining, CMA(3)-staining and 45S and 5 S fluorescence in-situ hybridization (FISH), we demonstrate that the 45S an d 5S ribosomal genes are clustered in two different chromosome pairs and bo th are located in heterochromatic GC-rich regions. PCR amplification and se quencing of the 5S intergenic non-transcribed sequences have allowed us to identify variability essentially due to a trinucleotide tandem repeat (GCT) .