In contrast to many other animals, knowledge about the canine karyotype is quite sparse. This is due in part to the rather difficult canine karyotypic pattern. Except for the X and the Y chromosome, there are only acrocentric chromosomes, which appear to be quite small and difficult to identify unambiguously. In previous reports, schematic representations of the canine karyotype have been described. However, a nomenclature comparable to that of the human karyotype or the karyotypes of sheep, cattle, or goats does not yet exist for the dog. Based on high-resolution banding of metaphase chromosomes from canine fibroblasts, we propose an ideogram of the canine karyotype with 460 numbered bands and characteristic landmarks. In addition, the centromere positions of the canine chromosomes are determined by a combined GTG-banding/ FISH approach, and the R- and G-banding patterns are compared.

Fragile sites were induced to expression in pig lymphocyte chromosomes by in vitro exposure to folate antagonists and BUdR-Hoechst 33258. Expressed fragility was localized according to the presented idiograms and compared with the location of known spontaneous translocations.

After fluorouracil/5-bromodeoxyuridine synchronization and subsequent FPG-staining, the karyotype of 15 phenotypically normal horses displayed several breaks and gaps. Twelve bands 1q24, 4p12, 8q23, 11p12, 16q21, 17q21, 23q31, 23q32, Xp21, Xq22, Xq25 and Xq27 showed relatively frequent fragility. After thymidine/cytidine synchronization and subsequent GWL-banding the same horses display karyotypes without any fragility. Hence it is suggested that the above listed bands harbour folate and/or 5-bromodeoxyuridine sensitive fragile sites.

No abstract

Using in situ hybridization, we have localized the human putative oncogene GLI to chromosome subbands 12q13.3-14.1. The precise genomic site is of interest since the region 12q13-15 has been found to be consistently rearranged in neoplasia-associated chromosome abnormalities in lipomas, myxoid liposarcomas, uterine leiomyomas, and pleomorphic adenomas of the salivary gland.