Capillary gel electrophoresis is the most common method for analysis of polymorphic short tandem repeats (STRs) loci used in forensic human identification. The procedure involves analysis of polymerase chain reaction (PCR)-amplified STR alleles in which 16 or more different loci may be simultaneously amplified in a single reaction, permitting a large amount of information to be obtained from a single sample extract. The system separates the amplified DNA based on variations in fragment sizes and detects each fragment using a series of fluorescent dyes attached to the 5' end of each amplicon during PCR. Capillary gel procedures can be multiplexed by using different dye labels, and multiple capillaries have been used to further increase sample throughput. The procedure is particularly valuable in mixture analysis. Specific techniques utilizing Y STRs for detection of male DNA and shorter amplicons for degraded DNA have also been developed. More recently, capillary systems have been miniaturized permitting the rapid detection of mitochondrial DNA as well as STRs. Future applications are currently being developed to permit simultaneous extraction, amplification, and detection on a single integrated device.
