Application of Ion Torrent PGM™ System in Detection of Fetal DNA in Maternal Plasma / 法医学杂志

OBJECTIVE@#To explore the feasibility of detecting of Y-STR of fetal DNA in maternal plasma using Ion Torrent PGM™ System.@*METHODS@#A total of 16 fetal DNA samples from maternal plasmas (8 cases from 38 weeks gestational age and 8 ones from 12 weeks) were prepared and a multiplex assay with 7 STR loci (DYS390, DYS391, DYS393, DYS438, DYS437, DYS456, DYS635) was designed for multiplex-PCR amplification. Using Ion Torrent PGM™ System, the results of Y-STR sequences and capillary electrophoresis were obtained and compared.@*RESULTS@#Y-STR specific alleles were detected in the maternal plasma of all the pregnant women having male babies of second and third trimester, which were higher than that detected by capillary electrophoresis. Consistent Y-STR genotypes were observed between fetal DNA from maternal plasma and genomic DNA from the newborn babies.@*CONCLUSION@#Based on Ion Torrent PGM™ System, the prenatal Y-STR detection method may provide a high-sensitive and high-throughput choice for prenatal STR detection in forensic testing.

Determination of the biological attribute of evidence at the scene using reverse transcription PCR and real-time fluorescent quantitative PCR / 法医学杂志

OBJECTIVE@#To explore the feasibility of biological method to identify the biological attribute of samples at crime scene.@*METHODS@#Thirty samples of ten blood stains, ten saliva stains and ten semen stains were selected, and all the samples were processed by the routine method and biomolecular method, respectively. Both RNA and DNA were isolated using DNA-RNA co-extraction technology and the mRNA was converted into cDNA using reverse transcription PCR (RT-PCR). Three pairs of specific primers were designed for blood stain, saliva stain and semen stain based on the different target genes in three specific tissues and the primers were amplified using real-time fluorescent quantitative PCR. The differences in these biological samples were evaluated by melting temperature (Tm) values and the size of the amplification fragment.@*RESULTS@#The Tm values of blood stain, saliva stain and semen stain were (84.5 +/- 0.2) degrees C, (76.9 +/- 0.3) degrees C and (88.5 +/- 0.2) degrees C, respectively. The length of PCR fragments of them was 177bp, 134bp and 294bp, respectively.@*CONCLUSION@#Compared with the routine method, RT-PCR with real-time fluorescent quantitative PCR is highly specific, sensitive and reliable to identify the biological attribute of evidence, and can be potentially applied to determine evidence attribute in forensic practice.

Comparative study of two methods of DNA extraction from different colour costal cartilage in STR genotyping / 法医学杂志

OBJECTIVE@#To compare the effectiveness of two methods of DNA extraction from different colour costal cartilages in STR genotyping.@*METHODS@#DNA fragments were extracted from costal cartilages of different colour of 30 corrupt corpses using Chelex-100 and Phenol-Chloroform methods. STR loci were analyzed by ABI 3100 genetic analyzer after PCR amplification by using Profiler Plus kit.@*RESULTS@#STR loci were completely detected in all 30 samlpes of costal cartilages when using Phenol-Chloroform DNA extraction methods. While using Chelex-100 methods, all STR loci were identified in 22 cases (11 white, 8 light-yellow and 3 yellow cases). Partial STR loci were detected in 7 cases (3 yellow and 4 yellow-brown cases) and none in 1 brown-black cases.@*CONCLUSION@#Suitable DNA extracion methods will be chosen depends on the colour of costal cartilage. Phenol-Chloroform methods is more effective in STR genotyping especially in dark colour costal cartilage cases.

Effect of PCR reaction volume on the accuracy of human identification tests / 法医学杂志

OBJECTIVE@#To investigate the effect of different PCR amplification volume on the accuracy of human identification test.@*METHODS@#Human genome DNA samples were amplified using ABI PRISM Profiler Plus kits in 50 microliters, 25 microliters, 12.5 microliters, and 6.25 microliters reaction volume, respectively. The thermocycle parameters were the same. All PCR products were then electrophoresized on ABI PRISM 310 Genetic Analyzer, 377 DNA Sequencer, and 3100 Genetic Analyzer. Data were processed by ABI PRISM GeneScan and Genotyper software.@*RESULTS@#The less reaction volume, the more alleles losing or alleles adding observed.@*CONCLUSION@#Non-standard volume of PCR amplification reaction should be used carefully in human identification test, especially when the sample DNA quality is not so satisfied.