Localization of glucose-6-phosphate dehydrogenase in mouse and man by in situ hybridization: Evidence for a single locus and transposition of homologous X-linked genes

By hybridizing a tritiatcd human genomic probe (pGD3) to metaphase chromosomes in situ, we have localized the gene for glucose-6-phosphate dehydrogenase (G6PD) in both the human and mouse complement. The locus on the intact human X chromosome is close to the telomere on the long arm. confirming the assignment based on studies of an X/autosome translocation in human-mouse hybrids. Although the signahbackground ratio was reduced for the heterologous hybridization of the human probe to mouse metaphases, 20% of the grains were on the X chromosome and 93% of these were in the A region, relatively close to the centromere. The location of G6PD in mouse and man reflects inirachromosomal transposition of these homologous X loci. Genomic DNAs from mouse and man and from hybrids with human X/autosome translocations were digested with several restriction enzymes including EcoRl, Pstl, and Hpcill, and Southern blots were probed with ³²P-pGD3. The results of the analysis also confirm the human G6PD assignment and are consistent with a single copy of the locus in the haploid genome of both species.