A Comparative Chromosome Banding Analysis of the Ursidae and Their Relationship to Other Carnivores
Cytogenetics and Cell Genetics
Trypsin G-banded karyotypes of eight species of Ursidae were prepared from retrovirus-transformed skin fibroblast cultures. The banding patterns of all bears are highly conserved, even though their diploid numbers range from 42 to 72. A comprehensive analysis of the homologous banding patterns within the Ursidae and with a hypothesized ancestral carnivore karyotype permitted the reconstruction of three significant chromosomal reorganization events that occurred during the evolution of the modern ursids. The first was a multichromosomal fissioning away from the biarmed (2n = 44) primitive carnivore karyotype, leading to six species of the Ursinae subfamily (2n = 78). The second was a comprehensive chromosome fusion in the lineage that led to the Ailuropodinae (giant panda) subfamily (2n = 44). The third event was a second, independent, but less extensive, centromeric fusion occurring in the line that led to the Tremarctinae (spectacled bear) subfamily (2n = 52). Ursidae karyotypes are not only highly conserved within the family but also exhibit extensive chromosome banding homology with other carnivore families.
Nash, William G. and Stephen J. O'Brien. 1987. "A Comparative Chromosome Banding Analysis of the Ursidae and Their Relationship to Other Carnivores." Cytogenetics and Cell Genetics 45, (3-4): 206-212. https://nsuworks.nova.edu/cnso_bio_facarticles/368