Pericentromeric location of the telomeric DNA sequences on the European grayling chromosomes

The chromosomal characteristics, locations and variations of the C-band positive heterochromatin and telomeric DNA sequences were studied in the European grayling karyotype (Thymallus thymallus, Salmonidae) using conventional C-banding, endonucleases digestion banding, silver nitrate (AgNO3), chromomycin A(3) and 4',6-diamidino-2-phenylindole staining techniques as well as fluorescence in situ hybridization (FISH) and primed in situ labelling. Original data on the chromosomal distribution of segments resistant to AluI restriction endonuclease and identification of the C-banded heterochromatin presented here have been used to characterize the grayling karyotype polymorphism. Structural and length polymorphism of the chromosome 21 showing a conspicuous heterochromatin block adjacent to the centromere seems to be the result of the deletion and inversion. Two pairs of nuclear organizer regions (NOR)-bearing chromosomes were found to be polymorphic in size and displaying several distinct forms. FISH with telomeric peptide nucleic acid probe enabled recognition of the conservative telomeric DNA sequences. The karyotype of the thymallid fish is thought to experienced numerous pericentric inversions and internal telomeric sites (ITSs) observed at the pericentromeric regions of the six European grayling metacentric chromosomes are likely relics of the these rearrangements. None of the ITS sites matched either chromosome 21 or NOR bearing chromosomes.University of Warmia and Mazury in Olsztyn, Poland (0804.0809)info:eu-repo/semantics/publishedVersio

Cytologic ploidy determination in fish - an example of two salmonid species

The method of ploidy level determination depends on the equipment, expertise of the lab or farm staff, and on the material studied (fish species, specimens' age and size, etc.). The combination of some simple techniques can be very helpful for fast, reliable and inexpensive assessment of effects of genome manipulations. Among indirect methods the nucleoli quantification seems to be the most convenient one, except that it is limited to species possessing one locus of nucleolar organizer regions (NORs) (rainbow trout as an example). Species with multilocus NORs (like brook trout) need another method, for instance sizing of erythrocytes nuclei. These techniques can be useful for identification of products resulting from new approaches in biotechnology applied to fish culture, as polyploidisation or hybridisation, for characteristics of transformation levels of organisms found in the wild or those produced due to experimental treatments