Sizing short tandem repeat alleles in capillary array gel electrophoresis instruments

A 96-capillary array get electrophoresis Applied Biosystems 3700 instrument has been used to analyse AMPF/STR SGM Plus(TM) short tandem repeat (STR) l oci for forensic applications. This multiplex consists of ten STIR loci plu s the Amelogenin locus and currently forms the basis of the UK National DNA database that currently holds more than 1 million profiles. Of particular interest is the accuracy of allele designation that is determined by compar ison with standard control allelic ladder markers. Some loci have higher st andard deviations than others. In particular the high-molecular-weight HUMF IBRA alleles have high standard deviations of the order of 0.15 and it is t hese alleles that are most likely to be misdesignated. However, this risk i s minimised by the analysis of at least five different allelic ladders acro ss the array to estimate the mean size of each allele. In conjunction with this, a series of guidelines that can be programmed into expert systems are used to minimise risks of misdesignation. The efficacy of the procedures u tilised are tested by computer simulation and demonstrated to be robust.