Mitotic separation of two human X-linked genes in man--mouse somatic cell hybrids

SIX INTERSPECIFIC SOMATIC HYBRID CELL LINES WERE DERIVED FROM A MOUSE LINE DEFICIENT IN HYPOXANTHINE: guanine phosphoribosyltransferase (HGPRT) and human diploid cells with normal enzyme activity. Human HGPRT was present in all six hybrids and the clones derived from them. However, in two of the six, and in some clones from another two, human glucose-6-phosphate dehydrogenase (G6PD) was absent. Since the structural loci for both these enzymes are X-linked in man, these findings suggest that these two loci have separated quite frequently through chromosome breakage and that they must be rather far apart on the X chromosome.