THE CHROMOSOMAL DISTRIBUTION AND ORGANIZATION OF SHEEP SATELLITE-I AND SATELLITE-II CENTROMERIC DNA USING CHARACTERIZED SHEEP-HAMSTER SOMATIC-CELL HYBRIDS

A panel of sheep-hamster somatic cell hybrids containing single sheep chromosomes was used to study the chromosomal distribution and organiz ation of two families of sheep centromeric satellite DNA. This study s hows that the centromeres of the sheep metacentric chromosomes 1, 2 an d 3 differ in their organization and relative quantities of sheep sate llite I DNA. The results, when correlated with the proposed formation of these metacentric chromosomes by ancient Robertsonian translocation s, suggest a loss or replacement of satellite I centromeric DNA from t he centromeres of these sheep chromosomes. Using Southern blot analysi s and fluorescence in site hybridization, this study shows that the re cent centric fusion chromosome t2 (rob 9;10) contains little satellite II DNA. Together these results suggest the possibility of substantial reorganization of sheep centromeric DNA families after Robertsonian t ranslocations.