OBJECTIVE: To compare the concentration of teeth DNA extracted by three different pretreatment methods and to explore a simple, economical and practical pretreatment method with high concentration of extracted DNA from teeth. METHODS: A total number of 21 molars were collected from 7 corpses. The pretreatment of 3 molars from each individual was randomly performed by tooth crumb method, ball-milling method and liquid nitrogen milling method and 50 mg tooth crumb was weight and DNA was extracted by AutoMate Express forensic DNA extraction system. Subsequently, the concentration of DNA and corresponding STR genotyping of three methods were compared. RESULTS: The DNA concentration extracted by tooth crumb method, ball-milling method and liquid nitrogen milling method was 0.055 6-1.989 1 ng/μL, 0.036 6-1.175 6 ng/μL and 0.037 8-1.249 0 ng/μL, respectively. The DNA concentration obtained by tooth crumb method was higher (P < 0.05) and the success rate of STR genotyping was high. CONCLUSION Combined with AutoMate Express forensic DNA extraction system, tooth crumb method is an efficient and feasible method to extract DNA from teeth, which can be applied in forensic practice.
DNA/isolation & purification* ; DNA Fingerprinting/methods* ; Genotype ; Humans ; Tooth

Kinship testing is widely needed in forensic science practice. This paper reviews the definitions of common concepts, and summarizes the basic principles, advantages and disadvantages, and application scope of kinship analysis methods, including identity by state (IBS) method, likelihood ratio (LR) method, method of moment (MoM), and identity by descent (IBD) segment method. This paper also discusses the research hotspots of challenging kinship testing, complex kinship testing, forensic genetic genealogy analysis, and non-human biological samples.
DNA Fingerprinting ; Forensic Genetics/methods* ; Forensic Sciences ; Pedigree ; Humans

OBJECTIVES: To investigate the efficacy of different numbers of microhaplotype (MH) loci and the introduction of different reference samples on the identification of full sibling, half sibling and differentiation between full sibling and half sibling kinships, and to explore the effect of changing mutation rate on sibling testing. METHODS: First, a family map involving three generations was established, and four full sibling identification models, five half sibling identification models and five models distinguishing full and half siblings were constructed for different reference samples introduced. Based on the results of the previous study, two sets of nonbinary SNP-MH containing 34 and 54 loci were selected. Based on the above MH loci, 100 000 pairs of full sibling vs. unrelated individuals, 100 000 pairs of half sibling vs. unrelated individuals and 100 000 pairs of full sibling vs. half sibling were simulated based on the corresponding sibling kinship testing models, and the efficacy of each sibling kinship testing model was analyzed by the likelihood ratio algorithm under different thresholds. The mutant rate of 54 MH loci was changed to analyze the effect of mutation rate on sibling identification. RESULTS: In the same relationship testing model, the systematic efficacy of sibling testing was positively correlated with the number of MH loci detected. With the same number of MH loci, the efficacy of full sibling testing was better than that of uncle or grandfather when the reference sample introduced was a full sibling of A, but there was no significant difference in the identification efficacy of the four reference samples introduced for full sibling and half sibling differentiation testing. In addition, the mutation rate had a slight effect on the efficacy of sibling kinship testing. CONCLUSIONS Increasing the number of MH loci and introducing reference samples of known relatives can increase the efficacy of full sibling testing, half sibling testing, and differentiation between full and half sibling kinships. The level of mutation rate in sibling testing by likelihood ratio method has a slight but insignificant effect on the efficacy.
Humans ; Siblings ; Polymorphism, Single Nucleotide ; DNA Fingerprinting/methods*

Objective To evaluate the efficiency of REPLI-g® Single Cell Kit for sample DNA amplification, and explore its application value in forensic trace DNA amplification. Methods Three DNA extraction kits were selected to extract DNA from peripheral blood of 10 unrelated individuals. The DNA yield and purity of the three DNA extraction kits were compared. According to the results of comparison, one DNA sample was selected to concentrate and dilute, then used as the initial sample of whole genome amplification （WGA）. REPLI-g® Single Cell Kit was used to amplify the initial sample at the whole genome level. The amplification yield and amplification times were calculated, and the distribution of DNA fragments was detected by agarose gel electrophoresis. Goldeneye® DNA ID System 20A Kit was used to perform the STR typing of the initial sample and DNA samples amplified at the whole genome level to evaluate the performance of REPLI-g® Single Cell Kit in trace DNA amplication in terms of purity and yield as well as the success rate of STR typing. Results After comparison, one DNA sample was selected from QIAsymphony® DNA Investigator® Kit extracts to concentrate and dilute as the initial sample of WGA. After amplifying the whole genome of a series of initial samples by REPLI-g® Single Cell Kit, the lowest average of amplification yield reached 8.77×103 ng, while the average of the corresponding amplification times reached 1.40×106. DNA fragments were large and concentrated. The STR typing success rate of WGA samples became lower with the decrease of initial samples used, but when the amount of samples was lower than 0.5 ng, the STR typing success rate of samples after DNA WGA was higher than that of samples without DNA WGA. Conclusion REPLI-g® Single Cell Kit can increase the yield of template DNA. Especially for trace DNA, the STR typing success rate can be improved to a certain extent.
DNA ; DNA Fingerprinting ; Humans ; Microsatellite Repeats ; Nucleic Acid Amplification Techniques/standards* ; Sequence Analysis, DNA/methods*

OBJECTIVE: To establish a method for whole genome amplification (WGA) based on (multiple displacement amplification MDA), and achieve DNA analysis of the human genome from low copy number (LCN). METHODS: DNA sample was used for WGA according to the REPLI-g kit protocol (QIAGEN, Germany). WGA product was used for DNA analysis according to the Applied Biosystems Profiler Plus kit protocol (ABI, USA). RESULTS: WGA product of DNA sample (10 pg) can be used for STR genotyping. CONCLUSION WGA technology could be helpful for LCN DNA analysis.
DNA/analysis* ; DNA Fingerprinting/methods* ; Genome, Human ; Genotype ; Humans ; Microsatellite Repeats ; Nucleic Acid Amplification Techniques/methods*

OBJECTIVE: To establish a method of fingerprint position, sample transfer and fingerprint DNA extraction in contact samples. METHODS: Sixty-six cases were visualized by 502 glue fingerprint fumigation. Two methods, ordinary wipe and acetone wipe, were used to transfer cast-off cells of fingerprints from testing samples, respectively. DNA was extracted and purified by ultramicro magnetic bead kit. The data was resolved on genetic analysis after amplification. RESULTS: In 33 samples, 30 samples got better STR analysis by acetone wipe method. The peak range was 1,000-4,000 RFU and peak shapes were equable. It was hard to get ideal STR typing by ordinary wipe method. CONCLUSION The samples are visualized by 502 glue fingerprint fumigation and the case-off cells are transferred by acetone wipe method. The method shows better STR analysis result, which might be a better method for forensic science practice.
Adhesives ; DNA/isolation & purification* ; DNA Fingerprinting/methods* ; Forensic Medicine ; Fumigation/methods* ; Humans

OBJECTIVES: To establish multiplex system of 16 miniSTR loci, and explore its application value for the degraded materials in forensic medicine. METHODS: The multiplex system of 16 miniSTR loci was established using a six-dye fluorescence labeling technology and its application value in forensic medicine was assessed. RESULTS: A six-dye fluorescence labeling miniSTR amplification kit was developed, which enabled 15 autosomal STR loci, Amelogenin locus and DYS391 to be typed simultaneously. This method showed good specificity and could provide stable and accurate typing results with a sensitivity of 50 pg. This system also provided a good test result for the normal biological sample of actual cases. CONCLUSIONS The multiplex system of 16 miniSTR loci has application value for degraded and trace materials with the advantages of high sensitivity and database compatibility, which can be used for forensic casework.
Amelogenin ; DNA Fingerprinting ; DNA Primers ; Forensic Medicine/methods* ; Microsatellite Repeats/genetics* ; Polymerase Chain Reaction

With the continuous development of DNA extraction and testing technology, the DNA left at a crime scene plays a decisive role in the determination of criminal suspects in criminal investigation. But in the meanwhile, the anti-reconnaissance awareness of suspect is growing, which leads to a decrease of evidence left at scene during and after a crime. Therefore, in the process of evidence collection at scene, the finding and extraction of touch biological evidence, and the DNA detection are more and more important. At present, the proportion of touch evidence at the crime scene increases, which plays an increasingly important role in the detection of cases. However, with the characteristics of minute quantities, small size and secrecy, these touch evidence is difficult to be observed. What's more, various forms of pollution at the scene greatly accelerate the degradation rate of trace material, thus, the test and analysis of such material has become the emphasis and difficulty of the forensic evidence identification. This article reviews different kinds, collection and extraction methods of touch DNA, the factors that affect the detection and the problems may meet in the detection for providing an application prospect to the forensic practice.
Crime ; Criminals ; DNA/isolation & purification* ; DNA Fingerprinting ; Forensic Genetics/methods* ; Humans ; Touch

OBJECTIVES: To collect single piece of dandruff with microscopes to improve the regular EZ-tape method for DNA extraction and genotyping, increase the utilization of samples, reduce the miss rate as well as the proportion of genotyping results of mixed stains. METHODS: The insides of the hats worn by two volunteers were stuck by EZ-tape and scotch tape respectively. DNA on EZ-tape was directly extracted using traditional method. Single piece of dandruff was collected from the scotch tapes under microscope. The two kinds of methods were both performed under continuous oscillation and standing digestion, respectively. DNA was extracted through Chelex-100 method, and STR genotypes were obtained after amplification and electrophoresis. The results of STR genotypes obtained by EZ-tape method and single piece of dandruff analytical method were compared. RESULTS: Miss detections happened in 11 samples （45.8%） by EZ-tape method and only single-source typing results were obtained. Ten samples （41.7%） showed the genotype results of mixed stain and six of which showed allele insertions and deletions. The genotype results were obtained successfully using the single piece of dandruff analytical method, and two samples showed mixed stain genotype. The number of exact typing processed by oscillation was higher than that by standing digestion （ P<0.05）. CONCLUSIONS The oscillation during the DNA extraction process is in favour of the DNA releasing. Single piece of dandruff analytical method can be used to obtain single-source STR genotype with high successful ratio and low miss rate. This method can be a collection method of special samples such as dandruff in forensic practice.
Alleles ; DNA/analysis* ; DNA Fingerprinting/methods* ; Dandruff/genetics* ; Genotype ; Humans ; Microsatellite Repeats ; Resins, Synthetic

OBJECTIVETo observe the unique DNA profile and the relationship between DNA profile and phenotype of Trichophyton rubrum,and establish an effective molecular method to identify T. rubrum.

METHODSThree primers, including (GACA)(4), (GTG)(5) and M13 core sequence (5'-GAGGGTG-GCGGTTCT-3'), were used to distinguish variations among 20 clinical isolates of T. rubrum and Trichophyton mentagrophytes.

RESULTSDifferent PCR-fingerprinting was seen between T. rubrum and T. mentagrophytes using three different primers. 2 stains of T. rubrum were identified among 6 supposed T. mentagrophytes.

CONCLUSIONST. rubrum can be distinguished using PCR, and (GACA)(4) is the most suitable primer.