OBJECTIVETo explore the mutations of 15 short tandem repeat (STR) loci in PlowerPlex16 System which are world-widely used in parentage testing.

METHODSMutations of 15 STR loci in PlowerPlex16 System were investigated in 1921 parentage testing cases from Chinese population.

RESULTSIn 1921 parentage cases, seventy cases (3.644%) were found to have mutations. Among these were one case with double mutations (D21S11 and PentaD) and another case with two different mutations (D7S820 and D16S539) in two children. The total number of mutated STR loci observed was 72 over 3764 meiosis with a mutation rate of 0.128% +/- 0.1104% x 10(-3). The highest mutation rate was 0.292% at vWA and D21S11. No mutation was observed at TH01 or at TPOX. The mutated alleles coming from father were five times more than those from mother. The majority (98.611%) of mutated alleles were the results of one-step mutation. The ratio of one-step gain versus loss was 1.826:1. There was only one multiple-step mutation with a double-repeat gain observed at PentaD locus. In the PlowerPlex16 System, nine loci, namely D8S1179, Penta D, D13S317, D16S539, D7S820, D5S818, D3S1358, TH01 and TPOX, have lower mutation rates and are more suitable for parentage testing.

CONCLUSIONMutation of STR is relatively common and often makes parentage testing more complicated. Selecting stable STR locus with low mutation rate is more important in parentage testing.