Study on forensic application of sequence variants in STR loci

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A number of sequence variants exists in STR (short tandem repeat) loci, HUMD21S11 and HUMD11S554, which offer many advantages for forensic investigation. Therefore, it is necessary to analyze not only amplified fragment sizes but also DNA sequences for the identification of those alleles. The probability of personal identification will be raised by detection of the sequence variants.First, to clarify the existence of the sequence variants in both STR loci in Japanese population. we sequenced 13 kinds of alleles for HUMD21S11 and 47 for HUMD11S554, which we detected in a total of about 500 unrelated Japanese individuals using the AMPFLP (amplified fragment length polymorphism) method. Consequently, the sequence variants were found in 9 kinds of alleles for HUMD21S11 and 16 for HUMD11S554. According to the method of Adams (1993), all of the sequences in HUMD11S554 were classified into 9 types including types IA^2, LA^3, IA^4 and IB^3 which were newly found in the present study.Secondly, … More for HUMD11S554, we sequenced 31 kinds of alleles detected in a total of 110 unrelated Hungarian Caucasian individuals and compared the sequence data between Japanese and Hungarian populations. As a result, some of the sequence types were different between both populations. Much more samples from both populations should be analysed to clarify whether those different sequence types originate in racial difference.Thirdly, to select the efficient method for detection of sequence variants, we analysed the alleles in which sequence variants existed in both loci using the direct sequencing method, the PCR-SSCP (single strand conformation polymorphism) method and the CFLP (cleavage fragment length polymorphism) method. Consequently, the direct sequencing method and the PCR-SSCP method were the most efficient one for the heterozygotic alleles and the homozygotic alleles, respectively.Lastly, we performed the sequence analyses of both loci for DNA samples from the forensic materials. In consequence, the sequence variants were successfully detected. The results show that sequence analyses of both loci are useful method for forensic investigations. Less