FISH MAPPING OF 3 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 chr omosomes of various species of bovidae family. We used three bovine X chromosome specific cosmid clones for fluorescence in situ hybridizati on mapping on cattle, goat, sheep, and river buffalo chromosomes to id entify homologous regions in the genomes of the four species. The thre e cosmids (cIOBT 314, 945, and 1489) mapped to well spaced locations o n buffalo X, and both arms of cattle X chromosome. However, of the thr ee probes, cosmids cIOBT 314 and 1489 showed no hybridization signal o n any of the goat-sheep chromosomes. Incidentally, the two cosmids sho w correspondence to those regions of the buffalo X chromosome which ar e proposed to be lost during the structural reshuffle of the latter, l eading to sheep/goat X chromosomes. The lack of hybridization signal o f the two cosmids in sheep and goat, therefore, indicates that these D NA sequences are most likely absent in the two genomes and probably co rrespond to the segments lost during evolution of their X chromosomes.