COMPOSITE PAGE - AN ALTERNATE METHOD FOR INCREASED SEPARATION OF AMPLIFIED SHORT TANDEM REPEAT ALLELES

Genetic typing of short tandem repeat (STR) loci may require electroph oretic separation techniques which, depending on the locus, can resolv e alleles differing in size by only 2, 3 or 4 base pairs (bps). Many s uch loci can be separated by horizontal, discontinuous polyacrylamide gel electrophoresis (hd-PA.GE). However, some loci present particular separation challenges. A composite (or step) gel system consisting of 2 zones, anodal and cathodal, which differ by pore size and ionic stre ngth, has been developed to augment resolution of DNA fragments withou t a need for additional electrophoretic equipment. Depending on pore s ize, as well as ionic strength, initial migration can be increased or decreased to effect resolution. When compared with hd-PAGE, this compo site gel electrophoretic system can result in enhanced resolution of P CR amplified STR alleles.