Abstract: Objective To seek simple and cost-effective extraction technique to improve multiplex STR amplification from minimal oral epithelial cell samples.Methods One hundred DNA samples of oral epithelial cells extracted by mini system Chelex-100 method were quantitated by ABI 7500 Real Time System and were then typed with IdentifilerTM system in ABI 3130 Genetic Analyzer.Results The DNA contents of different categories of samples were as followings:suck pipes(0.72-116.78 ng),cup edges(2.15-142.5 ng),mouths of drink bottle(1-34.65 ng),chopsticks(3.35-26.6 ng),fruit cores(0.294-21.4 ng),and poultry bones(0.88-5.88 ng).The mean successful typing rate for gender and more than 9 STR loci was about 59.38%.Except the addition or no addition of proteinase K to the samples,all other factors-C users' variation,sample extraction methods,and qualities and properties of the samples had considerable effects on the contents of extracted DNA.Conclusion Successful STR typing can be achieved in about 60% minimal oral epithelial cell DNA samples extracted by mini Chelex system.

Key words: forensic biology, oral epithelial cells, mini system Chelex-100 method, DNA quantitation, multiplex STR amplification