ORDERED RESTRICTION MAPS OF SACCHAROMYCES-CEREVISIAE CHROMOSOMES CONSTRUCTED BY OPTICAL MAPPING

A light microscope-based technique for rapidly constructing ordered ph ysical maps of chromosomes has been developed. Restriction enzyme dige stion of elongated individual DNA molecules (about 0.2 to 1.0 megabase s in size) was imaged by fluorescence microscopy after fixation in aga rose gel. The size of the resulting individual restriction fragments w as determined by relative fluorescence intensity and apparent molecula r contour length. Ordered restriction maps were then created from geno mic DNA without reliance on cloned or amplified sequences for hybridiz ation or analytical gel electrophoresis. Initial application of optica l mapping is described for Saccharomyces cerevisiae chromosomes.