[Allele-specific PCR and its application in forensic science].

Allele-specific polymerase chain reaction (AS-PCR) is a technique based on allele-specific primers, which can be used to analyze single nucleotide polymorphism (SNP) effectively including the transition, transversion and insertion/deletion polymorphism and has been exploited in the study of diseases research, molecular diagnosis, and forensic biological evidence. The article systematically reviews the principle, the detection methods, improvement of AS-PCR, and its research updates in the fields of autosome, Y chromosome and mitochondrial SNP, as well as its application in forensic science.

[AS-PCR assay for 20 mtDNA SNP typing and haplotype frequency].

OBJECTIVE: To develop a multiplex allele-specific PCR (AS-PCR) assay with three-color fluorescence labeling for mitochondrial DNA (mtDNA) SNP typing. METHODS: Based on the principle of AS-PCR, the primer sets were designed for 20 SNP located on the coding region of mtDNA and divided into 2 groups labeled with FAM and HEX fluorescence, respectively. A primer set included two forward (reverse) allelic specific primers with different sizes and a generic reverse (forward) primer. Blood samples from 200 unrelated individuals were analyzed by AS-PCR and capillary electrophoresis. Three random samples at least for each SNP site were examined and verified by direct sequencing. The haplotype frequency was investigated. RESULTS: Distinct electropherograms of 200 blood samples were obtained successfully. The typing results of direct sequencing were identical to those obtained from AS-PCR. The minimum detectable DNA concentration was 0.2 pg under the system of 10 microL. The sensitivity of the DNA concentrations ranged from 0.5 to 5 pg. The 200 individuals were assigned into 15 haplotype, and the haplotype diversity was 0.906 0. CONCLUSION: AS-PCR is a simple, rapid and efficient method for mtDNA SNP typing, and can be applied to forensic practice.

[Establishment of the multiplex genotyping system for 16 SNP loci on mtDNA].

OBJECTIVE: To establish a multiplex genotyping system of mtDNA SNP. METHODS: A multiplex analysis system of 16-plex mtDNA SNP loci was established with allele specific PCR and capillary electrophoresis genotyping technology. Fifty samples from unrelated Chinese Han individuals were typed with the multiplex system. The multiplex assay was validated by comparing with the direct sequencing method. RESULTS: The genotypes of all 50 samples were correctly determined by the multiplex system. The optimal genotypic graphs were obtained with an input DNA of 0.5-10 pg, and the typing results were completely consistent with those by direct sequencing method. CONCLUSION: The established multiplex system by allele specific PCR has high sensitivity, operational simplicity and high accuracy. It provides an effective and high output method for mtDNA SNP typing.

[Genetic polymorphisms of the dinucleotide STR locus D6S261].

OBJECTIVE: To investigate the application of dinucleotide STR locus in paternity testing. METHODS: Dinucleotide STR locus D6S261 was selected and the paternity testing blood samples were amplified using 200 random blood samples, 16 family samples and 193 paternity test samples. Data of the PCR products were collected by 3130XL Genetic Analyzer and the genetic parameters of population were calculated by PowerStats v12. RESULTS: Fifteen alleles and 50 genotypes were found and H, DP, PE and PIC were 0.850, 0.953, 0.695, and 0.820, respectively. The typing results of both family samples and paternity test samples were accord with the law of inheritance, which no mutation was discovered. CONCLUSION: The genetic polymorphisms of D6S261 show good characteristics with low mutation rate and high stability. It can be an effective method to solve the indetermination caused by mutation in paternity testing if the stutter bands can be decreased.