Cytogenetic study of the Bison bonasus; I: Identification of heterochromatic regions and NORs in European bison karyotype and comparison with domestic cattle (Bos taurus)

Abstract

The karyotypes of European bison Bison bonasus and domestic cattle Bos taurus are characterized by a diploid number of chromosomes, 2n = 60. Here, we characterized the European bison karyotype in terms of size and distribution of constitutive heterochromatin blocks (C-bands) and the location and number of nucleolar organizer regions (NORs), results were compared with those obtained for domestic cattle. For this purpose, staining for C and NOR bands was performed. In the chromosomes of both species, C-bands were located in the centromeric region of all chromosomes analyzed, except for the X chromosome. Active NORs in European bison chromosomes were identified in the chromosomes from pairs 2, 3, 4, 25, and 28. In cattle, NORs were located in chromosomes from pairs 2, 3, 4, 11, and 25. The average number of NORs in the cell of European bison and cattle was 4.47 ± 1.74 and 4.56 ± 1.66, respectively. The obtained results shed new light on the European bison cytogenetics and confirmed the high similarity between studied species.