Genetic typing of short tandem repeat (STR) loci may require electrophoretic separation techniques which, depending on the locus, can resolve alleles differing in size by only 2, 3 or 4 base pairs (bps). Many such loci can be separated by horizontal, discontinuous polyacrylamide gel electrophoresis (hd-PAGE). 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 strength, has been developed to augment resolution of DNA fragments without a need for additional electrophoretic equipment. Depending on pore size, as well as ionic strength, initial migration can be increased or decreased to effect resolution. When compared with hd-PAGE, this composite gel electrophoretic system can result in enhanced resolution of PCR amplified STR alleles.
- Composite gels