The single most polymorphic STR Locus: SE33 performance in U.S. populations

The STR locus SE33 (ACTBP2) located on chromosome 6 (6q14) is arguably the most polymorphic marker examined thus far by the forensic community with a heterozygosity of >0.95 in some populations. Three different primer sets were utilized in this study in order to assess the possibilities of primer binding site mutations. Population variation was measured in 460 U.S. Caucasian, 445 African American, 336 Hispanic, and 202 Asian samples along with mutation rates from almost 400 father–son pairs. In addition, the 10 genomic DNA components in NIST Standard Reference Material SRM 2391b were sequenced and found to exhibit a variety of additional base changes, insertions, and deletions outside of the SE33 repeat region.     

Concordance study between the AmpFlSTR MiniFiler PCR amplification kit and conventional STR typing kits

The AmpFlSTR MiniFiler polymerase chain reaction amplification kit developed by Applied Biosystems enables size reduction on eight of the larger STR loci amplified in the Identifiler kit, which will aid recovery of information from highly degraded DNA samples. The MiniFiler Kit amplifies CSF1PO, FGA, D2S1338, D7S820, D13S317, D16S539, D18S51, and D21S11 as well as the sex-typing locus amelogenin. A total of 1308 samples were evaluated with both the MiniFiler and Identifiler STR kits: 449 African American, 445 Caucasian, 207 Hispanic, and 207 Asian individuals. Full concordance between Identifiler and MiniFiler Kits was observed in 99.7% (10,437 out of 10,464) STR allele calls compared. The 27 differences seen are listed in Table 1 and encompass the loci D13S317 (n = 14) and D16S539 (n = 10) as well as D18S51 (n = 1), D7S820 (n = 1), and CSF1PO (n = 1). Genotyping discrepancies between the Identifiler and MiniFiler kits were confirmed by reamplification of the samples and further testing using the PowerPlex 16 kit in many cases. DNA sequence analysis was also performed in order to understand the nature of the genetic variations causing the allele dropout or apparent repeat unit shift.     

Developmental validation of reduced-size STR Miniplex primer sets

This paper describes a developmental validation study of three Miniplex sets covering 12 of the 13 CODIS loci. As these new sets will be used for the analysis of degraded and low level DNA, the validation studies were performed using 100-125 pg of DNA, the lowest input level at which peak balance, peak intensity, and allele consistency were stable. To demonstrate the applicability of the Miniplex sets to forensic casework, these validation studies were completed in accordance with the Scientific Working Group on DNA Analysis Methods (SWGDAM). A range of tests were performed including studies of concordance with standard multiplex kits, sensitivity and reproducibility, and PCR amplification conditions. Additionally, studies of mixtures, nonhuman and environmentally degraded DNA, and simulated forensic samples were performed. Our results demonstrate that Miniplex STR amplification procedures are a robust and sensitive tool for the analysis of degraded DNA.     

Forensic value of 14 novel STRs on the human Y chromosome

We identified and characterized 14 novel short-tandem-repeats (STRs) on the Y chromosome and typed them in two samples, a globally diverse panel of 73 cell lines, and 148 individuals from a European–American population. These Y-STRs include eight tetranucleotide repeats (DYS449, DYS453, DYS454, DYS455, DYS456, DYS458, DYS459, and DYS464), five pentanucleotide repeats (DYS446, DYS447, DYS450, DYS452, and DYS463), and one hexanucleotide repeat (DYS448). Sequence data were obtained to designate a repeat number nomenclature. The gene diversities of an additional 22 Y-STRs, including the most commonly used in forensic databases, were directly compared in the cell line DNAs. Six of the 10 most polymorphic markers include the newly identified Y-STRs. Furthermore, these novel Y-STRs greatly improved the resolution of paternal lineages, above the level obtained with commonly used Y-STRs, in the European–American population.