Myotonic dystrophy: update on progress to define the gene.

Using standard likelihood linkage techniques, the gene for dystrophia myotonica has been localized to the proximal long arm of chromosome 19. Several large families provided the substrate for detecting linkage of restriction fragment length polymorphisms which were developed in the laboratory from flow-sorted chromosome 19 genomic libraries. In over 500 family members from five families only a single cross-over with ApoC2 was detected. Thus a useful probe for antenatal and preclinical diagnosis is now available. Details of the strategy employed within the framework of clinical diagnosis, genetic epidemiology and recombinant DNA techniques is described.