Chromosomal characteristics and distribution of rDNA sequences in the brook trout Salvelinus fontinalis (Mitchill, 1814)

摘要: Brook trout Salvelinus fontinalis (Mitchill, 1814) chromosomes have been analyzed using conventional and molecular cytogenetic techniques enabling characteristics chromosomal location of heterochromatin, nucleolus organizer regions (NORs), ribosomal RNA-encoding genes telomeric DNA sequences. The C-banding chromosome digestion with the restriction endonucleases demonstrated distribution heterogeneity heterochromatin in brook genome. sequences RNA genes, namely nucleolus-forming 28S (major) non-nucleolus-forming 5S (minor) rDNAs, were physically mapped fluorescence situ hybridization (FISH) primed labelling. minor rDNA locus was located on subtelo-acrocentric pair No. 9, whereas major loci dispersed 14 pairs, showing a considerable inter-individual variation number location. at different chromosomes. Multichromosomal (3–6 sites) NORs by silver nitrate (AgNO3) impregnation. All Ag-positive i.e. active corresponded to GC-rich blocks heterochromatin. FISH probe showed presence interstitial site (ITS) adjacent NOR/28S 11. This ITS presumably remnant rearrangement(s) leading genomic redistribution Comparative analysis data among several related salmonid species confirmed huge rRNA gene clusters