Karyotypic relationships among Equus grevyi, Equus burchelli and domestic horse defined using horse chromosome arm-specific probes.

Using laser microdissection we prepared a set of horse chromosome arm-specific probes. Most of the probes were generated from horse chromosomes, some of them were derived from Equus zebra hartmannae. The set of probes were hybridized onto E. grevyi chromosomes in order to establish a genome-wide chromosomal correspondence between this zebra and horse. The use of arm-specific probes provided us with more information on the mutual arrangement of the genomes than we could obtain by means of whole-chromosome paints generated by flow sorting, even if we used reciprocal painting with probe sets from both species. By comparison of our results and results of comparative mapping in E. burchelli, we also established the chromosomal correspondence between E. grevyi and E. burchelli, providing evidence for a very close karyotypic relationship between these two zebra species. Establishment of the comparative map for E. grevyi contributes to the knowledge of the karyotypic phylogeny in the Equidae family.