Short tandem repeat (STR) genotyping of keratinised hair. Part 2. An optimised genomic DNA extraction procedure reveals donor dependence of STR profiles

A feasibility study of short tandem repeat (STR) genotyping of telogen phase hairs in particular, and hair shaft in general, is presented. A number of extraction procedures in common use were investigated and the quantities of nuclear DNA (nuDNA) delivered were quantified via a real-time PCR assay. The extracts were subjected to two variations on AmpFlSTR Profiler Plus PCR amplification strategies (extended cycles, two rounds of PCR) and the genotypes compared. Nuclear DNA was found to persist in human hair shafts, albeit at very low levels. Full Profiler Plus profiles consistent with the hair donor were obtained from 100 mg hair shaft samples (bleached and unbleached). These were, however, mixed profiles, indicating low copy number (LCN) contamination in the extracts. Single telogen hair clubs and single hair shafts delivered partial profiles with usually only one allele of heterozygous loci. Telogen phase hairs yielded the same amount of nuDNA (and no more) as hair shafts (either anagen or telogen). Whether hair shafts dissolved or not in lysis buffer had no effect on either the quantitated yield of DNA or on the chance of obtaining a correct genotype. These results provide evidence that genomic DNA resides on the exterior of the hair shaft and we use this information to suggest an optimal procedure for nuDNA extraction from keratinised hair samples: soaking hairs in simple digestion buffers containing Tris-HCl, a salt and a chelating agent without prior cleaning of the hair shafts. It is proposed that cleaning removes most of the recoverable DNA. This procedure was applied to obtain genotypes from 3 cm hair shafts which matched reference profiles from the donors at up to 9 out of 10 AmpFlSTR Profiler Plus STR loci. When the genotyping success was measured by counting the number of matches between the two dominant alleles at each locus for each extract with the reference DNA profile of the hair donor, the success was found to be highly dependent on the donor. The number of matching alleles varied between not less than 10 for one donor to no more than two for another donor. These results may well be linked to the environmental experience of the hairs from each donor prior to removal.     

Development and validation of the AmpFlSTR MiniFiler PCR Amplification Kit: a MiniSTR multiplex for the analysis of degraded and/or PCR inhibited DNA

DNA typing of degraded DNA samples can be a challenging task when using the current commercially available multiplex short tandem repeat (STR) analysis kits. However, the ability to type degraded DNA specimens improves by redesigning current STR marker amplicons such that smaller sized polymerase chain reaction (PCR) products are generated. In an effort to increase the amount of information derived from these types of DNA samples, the AmpFlSTR MiniFiler PCR Amplification Kit has been developed. The kit contains reagents for the amplification of eight miniSTRs which are the largest sized loci in the AmpFlSTR Identifiler PCR Amplification Kit (D7S820, D13S317, D16S539, D21S11, D2S1338, D18S51, CSF1PO, and FGA). Five of these STR loci (D16S539, D21S11, D2S1338, D18S51, and FGA) also are some of the largest loci in the AmpFlSTR SGM Plus kit. This informative nine-locus multiplex, which includes the gender-identification locus Amelogenin, has been validated according to the FBI/National Standards and SWGDAM guidelines. Our results demonstrate significant performance improvements in models of DNA degradation, PCR inhibition, and nonprobative samples when compared to the AmpFlSTR Identifiler and SGM Plus kits. These data support that the MiniFiler kit will increase the likelihood of obtaining additional STR information from forensic samples in situations in which standard STR chemistries fail to produce complete profiles.     

Moment of Silence

The paper looks at the establishment of religion clause in the First Amendment to the US Constitution, and cases, e.g. Brown v. Gilmore, followed by Croft v. Perry and Sherman v. Koch, cases that relate to the concept of the “moment of silence” in educational institutions in which it was claimed that such events constitute a breach of the establishment clause. Courts have been inconsistent in their decision-making, which may indicate a lack of transparency not only in the interpretation of the relevant phrase in the Constitution but also in the judicial interpretation of the “three-pronged test” with regard to “excessive entanglement” as laid out in Lemon v. Kurtzman of 1971. The paper discusses the “moment of silence” within the framework of a model of silence in which this type of silence would be labeled as either textual or situational silence.