The localization ofG6pd, glucose-6-phosphate dehydrogenase, andmdx, muscular dystrophy in the mouseXchromosome

Summary A low activity mutant of glucose-6-phosphate dehydrogenase, G6pd a-m1Neu has been used to position G6pd in the mouse X chromosome. Linkage tests with tabby , Ta and harlequin , Hq , indicate a likely gene order of Hq–G6pd–Ta . Muscular dystrophy, mdx , has been located by two-and three-point crosses using Hprt , Pgk-1 and Mo blo and suggest a gene order of Hprt–mdx–Pgk-1–Mo blo . Together with existing linkage data a tentative order for the seven loci is Hq–Hprt–G6pd–mdx–Ta–Pgk-1–Mo blo . The relative positions of G6pd and mdx have not been directly tested and G6pd is assigned provisionally proximal to mdx . In the three point test using Hq , G6pd and Ta the recombination frequency found between Hq and Ta was 9·9 ± 2·6%, substantially less than the value of 20·5 ± 2·1% reported by Isaacson et al. (1974).