DNA Commission of the International Society of Forensic Genetics (ISFG): an update of the recommendations on the use of Y-STRs in forensic analysis

The DNA Commission of the International Society of Forensic Genetics (ISFG) regularly publishes guidelines and recommendations concerning the application of DNA polymorphisms to the problems of human identification. A previous recommendation published in 2001 has already addressed Y-chromosome polymorphisms, with particular emphasis on short tandem repeats (STRs). Since then, the use of Y-STRs has become very popular, and a numerous new loci have been introduced. The current recommendations address important aspects to clarify problems regarding the nomenclature, the definition of loci and alleles, population genetics and reporting methods.     

Analysis of artificially degraded DNA using STRs and SNPs--results of a collaborative European (EDNAP) exercise

Recently, there has been much debate about what kinds of genetic markers should be implemented as new core loci that constitute national DNA databases. The choices lie between conventional STRs, ranging in size from 100 to 450 bp; mini-STRs, with amplicon sizes less than 200 bp; and single nucleotide polymorphisms (SNPs). There is general agreement by the European DNA Profiling Group (EDNAP) and the European Network of Forensic Science Institutes (ENFSI) that the reason to implement new markers is to increase the chance of amplifying highly degraded DNA rather than to increase the discriminating power of the current techniques. A collaborative study between nine European and US laboratories was organised under the auspices of EDNAP. Each laboratory was supplied with a SNP multiplex kit (Foren-SNPs) provided by the Forensic Science Service, two mini-STR kits provided by the National Institute of Standards and Technology (NIST) and a set of degraded DNA stains (blood and saliva). Laboratories tested all three multiplex kits, along with their own existing DNA profiling technique, on the same sets of degraded samples. Results were collated and analysed and, in general, mini-STR systems were shown to be the most effective. Accordingly, the EDNAP and ENFSI working groups have recommended that existing STR loci are reengineered to provide smaller amplicons, and the adoption of three new European core loci has been agreed.     

New multiplexes for Europe-amendments and clarification of strategic development

Recently, the ENFSI/EDNAP groups issued advice on the design of the next generation of STR multiplexes in order to encourage standardisation within Europe. As the result of collaborative experimentation within the EDNAP group, we demonstrated that the low molecular weight STRs had substantial benefits to detect degraded samples. We subsequently recommended adoption of three new mini-STR loci to improve the success rate of degraded DNA markers, concurrent with the reduction in size of the existing STR markers in current use. This also improves the discriminating power of the system which is important to improve the power of national DNA databases. Subsequent discussions have occurred with manufacturers and members of the ENFSI/EDNAP groups. Because significant time and investment is required to develop new multiplexes of 13+ STR loci, manufacturers indicated that it would be preferable to adopt a staged approach. Two differing, but parallel strategies have now emerged. The first strategy employs a 13 STR loci multiplex incorporating three mini-STRs into the current multiplex test. The second strategy employs a multiplex of six high molecular weight STRs (in current use), modified to provide smaller amplicons combined with an additional two loci of high discriminating power. Eventually, the two strategies will converge to provide a single multiplex of 15 STR loci. The process will be guided by the ENFSI/EDNAP groups.     

Dynamic Tempered Transitions for Exploring Multimodal Posterior Distributions

George Casella Department of Statistics, University of Florida, Griffin-Floyd Hall, P.O. Box 118545, Gainesville, FL 32611 e-mail: casella{at}stat.ufl.edu Multimodal, high-dimension posterior distributions are wellknown to cause mixing problems for standard Markov chain MonteCarlo (MCMC) procedures; unfortunately such functional formsreadily occur in empirical political science. This is a particularlyimportant problem in applied Bayesian work because inferencesare made from finite intervals of the Markov chain path. Toaddress this issue, we develop and apply a new MCMC algorithmbased on tempered transitions of simulated annealing, addinga dynamic element that allows the chain to self-tune its annealingschedule in response to current posterior features. This importantfeature prevents the Markov chain from getting trapped in minormodal areas for long periods of time. The algorithm is appliedto a probabilistic spatial model of voting in which the objectivefunction of interest is the candidate's expected return. Wefirst show that such models can lead to complex target formsand then demonstrate that the dynamic algorithm easily handleseven large problems of this kind.     

A comparison of adjustment methods to test the robustness of an STR DNA database comprised of 24 European populations

An aim of the European Network of Forensic Science Institutes (ENFSI) is to produce a DNA database of second generation multiplex (SGM) STR profiles that is representative of the resident cosmopolitan populations. To achieve this, data were collected from 24 different populations. All of the data were combined to form one database of 5700 profiles from which allele proportions were calculated. The robustness of this combined European database was tested by estimating parameter d for every DNA profile, where d=log(10)(Pm(c)/Pm(E)) Pm(c) is the match probability of the profile calculated from its cognate database and Pm(E) is the match probability of the combined European database. Overall there was a small tendency for Pm(c)>Pm(E) primarily because of sampling bias. This bias was removed by the simple expediency of applying an adjustment factor to the calculation of Pm(E). These were selected from the Balding size bias correction, the Balding and Nichols Fst correction, a minimum allele proportion (between 0.01 and 0.02), an upper bound of a 95% confidence interval (CI) and a lower bound on the genotype match probability. It was demonstrated that a single European database is a feasible proposition. A combination of different adjustment methods can be used to ensure that the result is conservative relative to the cognate database, and their effect measured by parameter d.     

‘Great Expectations’: Rehabilitating the Recalcitrant War Poets

Formulating a definition of ‘good’ poetry is, and should be, impossible. Yet women's poetry of the First World War seems generally to have been condemned as ‘bad’. It inspires an ambiguous response from readers who recognize the value of its historical, social and psychological content, but shudder at the limitations of its form. However, I believe that a much more fruitful reading of these ‘recalcitrant’ texts is possible. It is not my intention to deny either their problematic nature, or the diversity and complexity of male responses to the war, but rather to emphasize that women's experience of the First World War was radically different from that of men, and we should not therefore be constrained by the traditional parameters of 1914-18 criticism when we explore these works. This article examines a selection of this poetry in the light of the psychological processes of grief and bereavement, and in so doing indicates other areas in which constructive readings of these texts might be made.Why do we expect the articulation of a radically new and uniformly consistent poetic voice from what was a large and diverse group of women? The expectations of modernism ironically have created a literary ‘mainstream’ out of a selection of experimental, and largely male, writing. I hope to show that the ‘failure’ of these women to conform to our textual ‘great expectations’ is irrelevant. The single most characteristic feature of these women's experience of war was isolation. Their position had neither the homogeneity of the trenches, nor the intense intellectualism of experimental circles. Predominantly middle class, alienated by absence and bereavement, they attempted to articulate the unprecedented nature of their experience. That their experiments were not wholly successful is perhaps indicative of the near impossibility of the task they undertook.     

Exclusion of a man charged with murder by DNA fingerprinting

DNA fingerprinting was used to demonstrate that two murder-rapes committed in 1983 and 1986, respectively, were connected. The probability of chance association of the fingerprint was calculated as 5.8 x 10(-8). The man who had been charged with the murder was excluded because his DNA fingerprint did not match sperm DNA fingerprints obtained from swabs and clothing attributed to the two victims.