| Summary: | 碩士 === 國立臺灣大學 === 法醫學研究所 === 103 === Forensic genetics has been currently using PCR based Short Tandem Repeat (STR) polymorphisms. However, STR can be non-informative when DNA samples are degraded. Recent advances in single nucleotide polymorphisms (SNPs) research have raised the possibility that the SNP markers could replace the STR in analyzing degraded DNA samples. The purpose of this study was to develope an effective SNPs panel to genotype degraded DNA samples.
We collected 16 blood samples and 17 pacenta samples of Han Taiwanese (including 2 families with 3 trio and 1 duo sets). DNA was extracted and degraded to <100bp by DNase I treatment. Then qPCR quantification and STR genotyping were performed. The STR typing of degraded DNA showed gradually degradation signal pattern from shorter size STR loci to longer size, eventhough disappeared. The DNA fragments distribution was analyzed using Bioanalyzer and the length of DNA fragments revealed below 15 bp. Finally, a panel including 145 autosomal SNP loci was used to analyze degraded DNA by matrix-assisted laser desorption/ionization time of flight mass spectrometer (MALDI-TOF MS). The target amplicons for each 145 SNPs arranged from 60 bp to 100 bp.
Among the 145 SNP loci, 46% and 60% of genotypes could be successfully identified in 30 min and 60 min degeaded DNA samples. There were 51 SNP loci with detection rate above 50% for both 30min and 60min degraded samples. The total power of discrimination (Pd) was 0.9999999999, the cumulative probability of exclusion (CPEtrio) of trios-testing was 0.9999999999, and the cumulative probability of exclusion of duo-testing (CPEduo) was 0.999999. Compared to STR loci, these SNP loci offered a more informative analysis for degraded DNA in real parentage testing. In conclusion, this 145 SNP loci panel can be helpful in the analysis of degraded DNA and individual identification.
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