Levels of conservation and variation of heterochromatin and nucleolus organizers in the Bovidae

Abstract

Chromomycin A3 banding of the mitotic sets of 10 species of Bovidae (cattle, wisent, yak, banteng, gaur, red buffalo, swamp buffalo, sheep, mufflon, and goat) serves to demarcate both centromeric constitutive heterochromatin and R-banding patterns capable of identifying all the chromosomes within a given complement. In all species significant amounts of chromomycin-bright heterochromatin are present at the centromeres of all autosomes, though there was a high degree of intra- and inter-individual variation in the size of the heterochromatic blocks. Marked interspecies differences in the centromeric patterns were evident. The X chromosomes contained appreciable amounts of centromeric heterochromatin only in the two buffaloes. All the animals studied lacked distamycin A - diamidinophenylindole type heterochromatin. AgNO3 staining was applied sequentially to detect the location of active nucleolus organizer regions (NORs). The distribution of NORs was reasonably conservative in most of the species. An exceptional situation was found in the two buffaloes, where only one NOR pair matched with the standard karyotype of the Bovidae.