Cytogenetic and physical mapping in the region of the X chromosome surrounding the fragile site.

Seven DNA probes have been mapped within the Xq27-Xq28 region using in situ hybridization, in some cases on chromosomes expressing the fragile site to enhance the resolution. To complement these studies and investigate the relationship between genetic, cytogenetic and physical distance some of these probes were used for large scale mapping using pulsed field gels. Physical linkage was demonstrated between two loci, F9 and MCF2, which are separated by less than 270 kb, and a restriction map extending over 1,300 kb has been generated.