Horizontal two-dimensional electrophoresis of complex DNA samples using precast gel systems

We have developed a simplified procedure for the separation of enzyme-diges ted genomic DNA, or of complex mixtures of cloned DNA, into two dimensions. The procedure relies on the use of precast gels for horizontal electrophor etic separations. Precast agarose-type gels are used for the first-dimensio nal separation of fragments based on size. Precast polyacrylamide gels are used for the second-dimensional separationof fragments. The separated fragm ents are subjected to enzymatic digestion in situ prior to their transfer t o the second-dimensional gel. Applications of this procedure include the an alysis of DNA libraries, analysis of yeast artificial chromosomes (YACs) as well as other similar preparations, and the screening of genomic DNA for t he occurrence of multi-copy DNA fragments as in the case of genomic amplifi cations in cancer.