Natsuko Mizuno, Hiroaki Senju, Kazumasa Sekiguchi, Kanako Yoshida, Kentaro Kasai, Ikuko
Sakai, Hajime Sato and Sueshige Seta
National Research Institute of Police Science, Tokyo, Japan
Multiple DNA typings are required to achieve high accuracy of individual identification of degraded samples from which MCT118 and HLADQa types are not detected. AmpliType™ PM amplification and typing kit enables us to type five loci simultaneously by using reverse dot hybridization technology. Because PCR products of five loci of PM tests are smaller than those of HLADQa, it is expected that PM typing can be performed with degraded samples. However, the loci have only two or three alleles and it is difficult to detect PM types accurately from mixed DNA. Therefore, we investigated the detection of PM types from mixed samples and a degraded sample.
PM loci were detected from DNA samples mixed at various ratios from 2 different individuals. Types of all loci from major DNA were determined at the ratio of 1:7, because apparent differences in dot intensities among alleles were observed. At the ratio of 49:1 color intensities derived from minor DNA were weaker than the S dot.
PM typing was performed from bloodstains on gauze, paper and cotton stored at laboratories room over a period of time from 15 to 34 years. From 15 and 17 year-old bloodstains all loci could be typed. Strong dot intensities on PM loci without the visible S dot were observed from more than 17-year-old bloodstains. GC locus was most robust among the five. To correctly determine PM types in case of S dot absence it is strongly requested to apply a control system for each locus other than the S dot.
As a technical strategy of PM typing, two criteria are raised. One is that PM typing from mixed DNA extracted from contaminated evidential samples should not be carried out and another is that control DNA should be used as each locus standard for reading the strips without the visible S dot.
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