Establishment Of The STR Loci Multiplex PCR System And Its Application In Forensic Medicine

Objective:More human autosomal supplementary STR loci were screened,and a multiplex amplification detection system including the screening STRs was established.Forensic application evaluation and population genetics investigation will be performed on this system.This system provided new detection markers and detection methods for individual identification and complex relationship identification.Methods:1.We screened STR loci that meet the requirements for forensic applications for 22 pairs of autosomes by using the Ensembl genome database of the European Bioinformatics Institute and the human genome browser of the University of California Santa Cruz.2.On the basis of one CODIS STR locus(D2S1338)and one sex identification gene Amelogenin,18 new found autosomal STR loci and one Y-STR locus(DYS391)were added into the system.A multiplex fluorescence of PCR amplification detection system consisting of five color fluorescent markers was established by optimizing the multiplex amplification system and the reaction procedure.3.The sensitivity,specificity,stability and accuracy of the compound amplification system were evaluated by forensic science,and the population genetic parameters were investigated.Results:1.In this study,independent 35 autosomal STR loci that meet the requirements for forensic applications were screened from the entire genome of the human,and therein 18 STR loci were selected to successfully established fluorescent multiplex amplification system.2.The SiFaSTR 21plex NC composite amplification system was able to get complete typing when the DNA template volume was as low as 0.125 ng,and non-human genomic DNA contaminated samples would not interfere the typing of human genomic DNA.Thus,it had high sensitivity,good specificity,high repeatability and accuracy.3.The allele frequency and basic forensic parameters of the 20 loci were obtained from 532 unrelated individuals.A total of 182 alleles at 18 newfound autosomal STRs were observed among 532 individuals.No significant deviation from HWE was observed at the 18 newfound STRs in Chinese Han population after Bonferroni correction(p>0.05/18).The average heterozygosity of 19 autosomal STRs reached 0.7254,the polymorphism information capacity(expect D1S1616,D3S2457 and D8S1039)was more than 0.60,the average personal recognition probability reached 0.8862.Since 19 autosomal STR loci were independent from each other,the CPEduo and CPEtrio were calculated as exceeding 1-2.9×10-7 and 1-1.9×10-8,respectively.For the Y chromosome STR loci,the GD value of the DYS391 was 0.4113.Conclusion:This study screened 35 autosomal STR loci that meet the requirements for forensic applications and developed a multiplex fluorescence of PCR amplification detection system including 20 STRs and one Amelogenin.This system consists of 18 novel STRs with high polymorphisms.The present SiFaSTR 21 plex NC typing system would provide a supplementary powerful tool for forensic applications,which was useful for individual identification and complex relationship identification.