RESUMEN
Restriction endonuclease in situ digestion of metaphase chromosomes gives an opportunity to reveal strips with different structure within GC-rich pericentric heterochromatin of the domestic horse and the wild Przewalski horse. Blocks of heterochromatin, which are insensitive to HaeIII and brightly stained with chromomycin A3 after restriction enzyme digestion, are localized on the border with euchromatin in the majority of chromosomes of Equus caballus and E. przewalskii. In contrast to chromosome 5 of E. caballus, acrocentric chromosomes of E. prezewalskii which are homologous to this chromosome have RE-CMA-blocks. We discuss a possible nature of the specific heterochromatin, which is insensitive to restriction enzyme digestion, and its role in the karyotype evolution.
Asunto(s)
Heterocromatina/ultraestructura , Caballos/genética , Metafase , Animales , Desoxirribonucleasa HpaII , Desoxirribonucleasas de Localización Especificada Tipo II , Hibridación Fluorescente in Situ , CariotipificaciónRESUMEN
Heterochromatin distribution was studied in three species of subfamily Bovinae: bison (Bison bison), European bison (Bison bonasus), and gayal (Bos frontalis). In all of the studied species, C- and CMA3-banding and in situ hybridization with satellite DNAII (satDNAII) revealed the conservative distribution of heterochromatic regions in autosomes; sex chromosomes did not contain the classical constitutive heterochromatin. The Y chromosome was the most variable element of the karyotypes of both bison species and the gayal. A mechanism for formation of the acrocentric Y chromosome in B. bison was suggested. This hypothetical mechanism included breakage of the p arm at the telomeric region and subsequent translocation and inversion. The map of B. bison chromosomes (491 bands per haploid set) is presented. The data obtained are discussed in terms of speciation and the evolution of Bovinae karyotypes.