Janette W. Redman

Results from the NIST 2004 DNA Quantitation Study

For optimal DNA short tandem repeat (STR) typing results, the DNA concentration ([DNA]) of the sample must be accurately determined prior to the polymerase chain reaction (PCR) amplification step in the typing process. In early 2004, the National Institute of Standards and Technology (NIST) conducted an interlaboratory study to help assess the accuracy of DNA quantitation in forensic DNA laboratories. This study was designed with four primary purposes: (1) to examine concentration effects and to probe performance at the lower DNA concentration levels that are frequently seen in forensic casework; (2) to examine consistency with various methodologies across multiple laboratories; (3) to examine single versus multiple source samples; and (4) to study DNA stability over time and through shipping in two types of storage tubes. Eight DNA samples of [DNA] from 0.05 ng/microL to 1.5 ng/microL were distributed. A total of 287 independent data sets were returned from 80 participants. Results were reported for 19 different DNA quantitation methodologies. Approximately 65% of the data were obtained using traditional slot blot hybridization methods; 21% were obtained using newly available quantitative real-time PCR (Q-PCR) techniques. Information from this interlaboratory study is guiding development of a future NIST Standard Reference Material for Human DNA Quantitation, SRM 2372.

Analysis of mutations in father–son pairs with 17 Y-STR loci

We have examined 389 father/son sample pairs from U.S. Caucasians, African Americans, Hispanics and Asians using the 17 Y-STR loci in the Yfilertrade mark kit and observed a total of 24 differences between father and son. Thirteen mutations resulted in the gain of a repeat in the son and 11 resulted in a loss of a repeat. All samples resulted in single repeat mutations except one sample which contained a two repeat loss at Y-GATA-H4. Furthermore, two different sample pairs were found to have two mutations. An African American sample pair had a mutation at DYS458 and a second at DYS635 and an Asian sample pair had mutations at DYS439 and Y-GATA-H4.

NIST mixed stain studies #1 and #2: interlaboratory comparison of DNA quantification practice and short tandem repeat multiplex performance with multiple-source samples.

The Mixed Stain Study 1 (MSS1, Apr.-Nov. 1997) and Mixed Stain Study 2 (MSS2, Jan.-May 1999) evaluated multiplexed short-tandem repeat (STR) DNA typing systems with samples containing DNA from more than one source. These interlaboratory challenge studies evaluated forensic STR measurement, interpretation, and reporting practice using well-characterized samples of very different analytical difficulty. None of the relatively few errors reported in either exercise resulted in a false identification of a reference source; several errors in evaluating the unknown source in three-source samples would hinder matching the profile in any archival database. None of the measurement anomalies reported is associated with any particular STR multiplex; all DNA amplification anomalies are associated with inefficient DNA extraction, inaccurate DNA quantitation, and/or analytical threshold policies.

Turkish population data with the CODIS multiplex short tandem repeat loci

Allele frequencies for 13 tetrameric short tandem repeat (STR) loci, CSF1PO, D18S51, D3S1358, D21S11, D5S818, FGA, D7S820, HUMTH01, D8S1179, TPOX, D13S317, VWA, and D16S539 were determined on 198 Turkish blood samples.