Abstract
Utilising pulse-field gel electrophoresis physical linkage between three mouse X-linked genes has been demonstrated. The three genes, P3, G6pd and Cf-8 all lie within 400 Kb of DNA. This physical linkage mirrors the situation on the human X chromosome, representing the first demonstration of mouse/human synteny at the physical level. A detailed physical map encompassing 1.6 Mbp of this region is presented. A number of the rare cutter restriction enzyme sites within this map are partially blocked on the inactive X chromosome, presumably due to the methylation of CpG rich islands. Pulsed field gel electrophoresis therefore provides a useful tool for the study of X-inactivation over large regions of the X chromosome.