Investigation Of Genetic Polymorphism At 5 MiniSTR Loci And Analysis Of The Application In Forensic Medicine

Objective To investigate genetic polymorphism of D1S1677, D2S441, D4S2364, D6S1017and D9S2157 miniSTR loci in Shanghai population and analyze characterization of these loci in DNA highly degraded samples, 120 unrelated individuals samples from Shanghai and 7 DNA highly degraded samples were amplified. The efficience of the two different DNA analysis methods were compared. In addition, the value in a variety of scenarios, particularly for complex paternity case, were evaluated.Methods By use of the Chelex 100, DNA were extracted from 120 unrelated individuals blood stains, 7 hightly degraded samples and 3 blood stains for complex paternity testing. After quantification, the DNA were amplified by polymerase chain reaction(PCR), and the products were analyzised using 3130XL genetic analyzer and genemapper 3.2 software. The allele frequencies and genotype frequencies at 5 miniSTR loci were obtained from a sample of 120 unrelated individuals. Hardy-weinberg equilibrium were examined with Chi-square test. The Excluding Probability of Paternity (PE), Polymorphism Information Content(PIC), Power of Discrimination(PD) and Expected Heterozygosity(HE) were caculated by EXCEL software.Results 5 miniSTR loci successful amplified in the 120 unrelated individuals. Each locus, except D2S441, met Hardy-weinberg equilibrium perfectly. The loci of D1S1677 , D2S441, D4S2364, D6S1017and D9S2157 were detected allele 11,12,13,14,15,16;10,11,11.3,12,13,14,15,16; 6,7,8,9,10; 8,9,10,11,12,13,14,15; 11,12,13,14,15,16,17 respectively. The Excluding Probability of Paternity (PE), Polymorphism Information Content(PIC), Power of Discrimination(DP) and Expected Heterozygosity(HE) of D1S1677, D2S441, D4S2364, D6S1017 and D9S2157 loci in Shanghai population were 0.4055,0.6006,0.8162, 0.7882; 0.5343, 0.7179, 0.9025, 0.8657; 0.3657, 0.5816, 0.8094, 0.8157; 0.4585, 0.6576, 0.8618, 0.8104; 0.5439, 0.7265, 0.8892, 0.8925 repectively。Among the five miniSTR loci, D9S2157 showed the highest PIC (0.7265), PE (0.5439) and HE(0.8925) than other loci presented. We genetyped the complex paternity samples with the 5 miniSTR loci, and another deviated locus was found again between the son and the No 2 suspected father. 3 of the 7 degraded samples which failed to genotyped with the commercial STR kit were all successfully amplified with the 5 miniSTR loci. The number of loci detected from these 7 degraded samples were 5, 4, 4, 5, 5, 0, 0 repectivley. Significant differences(P<0.005) was detected between commercial kit and Miniplexes, that proved miniSTR technique was more efficient than the conventional STR method when degraded samples were tested.Conclusion1. The 5 miniSTR loci successful amplified in the 120 unrelated Shanghai individuals that the DNA database of the five loci are created.2. The five miniSTR loci are high polymorphism with the accumulated PE, DP and PM value of 95. 66%, 0.99995 and 5.23×10-5 respectively, they will serve as useful complement to the CODIS loci in forensic paternity testing3. 5 of the 7 DNA degraded samples were genetyped successfully that prove miniSTR technique is helpful for highly degraded samples in forensic medicine.