Evaluation of a quadruplex short tandem repeat system (HUMVWA31/A, HUMD11S554, HUMAPOAI1, and HUMACTBP2 loci) for forensic identity testing, confident typing of complex alleles, and population databases

Aim. To evaluate a quadruplex short tandem repeat (STR) system based on the amplification of allelic products from HUMVWA31/A, HUMD11S554, HUMACTBP2, and HUMAPOAI1 loci for routine identity testing in forensic casework, and t o provide details for the construction of a "multiplex allelic ladder" for confident typing of complex alleles from the quadruplex STR system and comp iling a database for three representative populations living in Northern No rway (Norwegian, Saami, and Russian/Ukrainian). Methods. The constructed "multiplex allelic ladder" consisted of 44 regular ly spaced and uniform alleles, spanning from 135 to 333 bp and included 9 H UMVWA31/A alleles (TCTA repeat unit), 9 HUMD11S554 alleles (AAAG repeat uni t), and 26 HUMACTBP2 alleles (AAAG repeat unit). Confident typing of select ed complex alleles from the quadruplex STR system was secured only when the y were compared with their matching ladder composed of the same repetitive unit as in our constructed "multiplex allelic ladder". Using different fluo rescent dyes, PCR products from the quadruplex STR system were sized with c onstructed allelic ladder (red labeled) in one lane. Results. Population database was established for unrelated Norwegians (n=14 1), Saami (n=78), and Russians/Ukrainians (n=138). Combined paternity exclu sions were 99.86%, 99.94%, 99.95% and the values of probability of match we re 8.0x10(-8), 1.4x10(-8), and 1.1x10(-8), in Saami, Norwegians, and Russia ns/Ukrainians, respectively. Conclusion. We conclude that by applying our constructed allelic ladder a c onfident typing of alleles from our quadruplex STR system may be ensured. F urther, the high efficiency of the selected loci makes this system a reliab le tool for use in forensic casework.