NCJ Number
246764
Journal
Forensic Science International: Genetics Volume: 8 Issue: 1 Dated: January 2014 Pages: 143-146
Date Published
January 2014
Length
4 pages
Annotation
Several commercial multiplex PCR kits for the amplification of short tandem repeat STR loci have been extensively applied in forensic genetics.
Abstract
Several commercial multiplex PCR kits for the amplification of short tandem repeat STR loci have been extensively applied in forensic genetics. Consequently, large numbers of samples have been genotyped, and the number of discordant genotypes observed has also increased. We observed allele dropout with two novel alleles at the STR loci TH01 and D13S317 during paternity testing using the AmpF&STR Identifiler PCR Amplification Kit. The lost alleles reappeared when alternative PCR primer pairs were used. A sequence analysis revealed a G-to-A substitution 82 bases downstream of the last TCAT motif of the repeat region at the TH01 locus GenBank accession: D00269 and a G-to-T substitution 90 bases upstream of the first TATC motif of the repeat region at the D13S317 locus GenBank accession: G09017. The frequencies of these two point mutations were subsequently investigated in the Chinese population using sequence-specific primer PCR SSP-PCR, but neither of these mutations was detected in any of the samples tested. In addition, the DNA samples in which the mutations were identified were amplified to type the point mutations by SSP-PCR to determine the corresponding STR alleles at the two loci. Subsequently, the amplified PCR products with different point mutations and STR repeat numbers were directly sequenced because this strategy overcomes the appearance overlapping peaks generated by different STR alleles and accurately characterizes genotypes. Thus, our findings not only provide useful information for DNA databases and forensic identification but also establish an effective strategy for typing STR alleles with primer binding site mutations.