FISH mapping of three bovine cosmids to cattle, goat, sheep and buffalo X chromosomes

Contrary to extensive banding similarities of the autosomes, there are variations in the morphology as well as banding patterns of the X chromosomes of various species of bovidae family. We used three bovine X chromosome specific cosmid clones for fluorescence in situ hybridization mapping on cattle, goat, sheep, and river buffalo chromosomes to identify homologous regions in the genomes of the four species. The three cosmids (cIOBT 314, 945, and 1489) mapped to well spaced locations on buffalo X, and both arms of cattle X chromosome. However, of the three probes, cosmids cIOBT 314 and 1489 showed no hybridization signal on any of the goat-sheep chromosomes. Incidentally, the two cosmids show correspondence to those regions of the buffalo X chromosome which are proposed to be lost during the structural reshuffle of the latter, leading to sheep/goat X chromosomes. The lack of hybridization signal of the two cosmids in sheep and goat, therefore, indicates that these DNA sequences are most likely absent in the two genomes and probably correspond to the segments lost during evolution of their X chromosomes.