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Abstract Plant and animal karyotypes sometimes contain variable elements, that are referred to as additional or B-chromosomes. It is generally believed that B-chromosomes lack major genes and represent parasitic and selfish elements of a genome. Here we report, for the first time, the localization of a gene to B-chromosomes of mammals: red fox (Vulpes vulpes) and two subspecies of raccoon dog (Nyctereutes procyonoides). Identification of the proto-oncogene C-KIT on B-chromosomes of two Canidae species that diverged from a common ancestor more than 12.5 million years ago argues against the current view of B-chromosomes. Analyses of fox B-chromosomal C-KIT gene from a flow-sorted fox B-chromosome-specific library revealed the presence of intronexon boundaries and high identity between sequenced regions of canine and fox B-chromosomal C-KIT copies. Identification of C-KIT gene on all B-chromosomes of two canid species provides new insight into the origin and evolution of supernumeraries and their potential role in the genome. [ABSTRACT FROM AUTHOR]

Abstract Many canine tumour types represent useful models for tumours also found in humans. Studies of chromosomal abnormalities in canine tumours have been impeded by the complexity of the canine karyotype (2n = 78), which has made accurate identification of rearranged chromosomes difficult and laborious. To overcome this difficulty we have developed a seven-colour paint system for canine chromosomes, with six sets of chromosome paints covering all chromosomes except Y. Several pairs of canine autosomes co-locate in the flow karyotype. To distinguish these autosomes from each other, paint sets were supplemented with chromosomes of red fox and Japanese raccoon dog. Paints were used in fluorescence in-situ hybridization to analyse karyotypes in fourteen canine soft tissue sarcomas. Rearranged karyotypes were observed in seven tumours, but there was evidence for loss of rearrangement during tissue culture. Five tumours had rearrangements involving four chromosomes or fewer; one, a chondrosarcoma, had lost seven chromosomes whilst the last, a spindle cell sarcoma, had rearrangements involving eighteen chromosome pairs. The paint sets described here facilitate the complete cytogenetic analysis of balanced translocations and other inter-chromosomal rearrangements in canine tumours. We believe that this is the first canine tumour series to be subjected to this level of analysis. [ABSTRACT FROM AUTHOR]

Abstract We have made a complete set of painting probes for the domestic horse by degenerate oligonucleotide-primed PCR amplification of flow-sorted horse chromosomes. The horse probes, together with a full set of those available for human, were hybridized onto metaphase chromosomes of human, horse and mule. Based on the hybridization results, we have generated genome-wide comparative chromosome maps involving the domestic horse, donkey and human. These maps define the overall distribution and boundaries of evolutionarily conserved chromosomal segments in the three genomes. Our results shed further light on the karyotypic relationships among these species and, in particular, the chromosomal rearrangements that underlie hybrid sterility and the occasional fertility of mules. [ABSTRACT FROM AUTHOR]

Abstract Genome-wide homology maps among dog (Canis familiaris, CFA, 2n=78), African lion (Panthera leo, PLE, 2n=38), clouded leopard (Neofelis nebulosa, NNE, 2n=38) and Malayan sun bear (Helartos malayanus, HMA, 2n=74) have been established by chromosome painting using a complete set of dog probes. In total, chromosome-specific painting probes from the 38 dog autosomes reveal 69, 69 and 73 conserved segments in African lion, clouded leopard and Malayan sun bear, respectively. The chromosomal painting results show that the African lion and clouded leopard have an identical karyotype which, in turn, is similar to that previously published for the cat (Felis catus, FCA 2n=38). The findings confirm and extend other studies that show felids to be karyotypically conserved. In contrast, ursids, including the Malayan sun bear, have a relatively highly rearranged karyotype in comparison with other carnivores. The 2n=74 karyotype of the Malayan sun bear, which is believed to closely resemble the ancestral karyotype of the Ursidae, could have evolved from the 2n=42 putative ancestral carnivore karyotype by an inversion and 16 centric fissions. Independent fusions of the acrocentric ancestral chromosomes have generated the unique karyotypes of the giant panda and the spectacled bear. [ABSTRACT FROM AUTHOR]

We have made a complete set of painting probes for the domestic horse by degenerate oligonucleotide-primed PCR amplification of flow-sorted horse chromosomes. The horse probes, together with a full set of those available for human, were hybridized onto metaphase chromosomes of human, horse and mule. Based on the hybridization results, we have generated genome-wide comparative chromosome maps involving the domestic horse, donkey and human. These maps define the overall distribution and boundaries of evolutionarily conserved chromosomal segments in the three genomes. Our results shed further light on the karyotypic relationships among these species and, in particular, the chromosomal rearrangements that underlie hybrid sterility and the occasional fertility of mules. [ABSTRACT FROM AUTHOR]

Genome-wide homology maps among dog (Canis familiaris, CFA, 2n=78), African lion (Panthera leo, PLE, 2n=38), clouded leopard (Neofelis nebulosa, NNE, 2n=38) and Malayan sun bear (Helartos malayanus, HMA, 2n=74) have been established by chromosome painting using a complete set of dog probes. In total, chromosome-specific painting probes from the 38 dog autosomes reveal 69, 69 and 73 conserved segments in African lion, clouded leopard and Malayan sun bear, respectively. The chromosomal painting results show that the African lion and clouded leopard have an identical karyotype which, in turn, is similar to that previously published for the cat (Felis catus, FCA 2n=38). The findings confirm and extend other studies that show felids to be karyotypically conserved. In contrast, ursids, including the Malayan sun bear, have a relatively highly rearranged karyotype in comparison with other carnivores. The 2n=74 karyotype of the Malayan sun bear, which is believed to closely resemble the ancestral karyotype of the Ursidae, could have evolved from the 2n=42 putative ancestral carnivore karyotype by an inversion and 16 centric fissions. Independent fusions of the acrocentric ancestral chromosomes have generated the unique karyotypes of the giant panda and the spectacled bear. [ABSTRACT FROM AUTHOR]