DXS10079, DXS10074 and DXS10075 are STRs located within a 280-kb region of Xq12 and provide stable haplotypes useful for complex kinship cases

The evaluation of the short tandem repeat (STR) markers DXS10079, DXS10074 and DXS10075 was amended to establish a STR cluster spanning a genetic distance<1 cM. These three STRs are located within a 280-kb region at Xq12 and provide stable haplotypes useful for solving complex kinship cases. Theoretically, this cluster could give rise to 2,548 different haplotypes in the German population and the genotyping of 781 men revealed the presence of 172 haplotypes. Since the three STRs were shown to be in strong linkage disequilibrium (LD), haplotype frequencies cannot be computed on the basis of a single locus allele frequency alone but have to be estimated directly. Here, we present data on linkage, haplotype frequencies and LD in a German population. Further clusters from other regions of the X chromosome will be published in the future to cover the chromosome with a well-structured network of highly informative sites.

Forensic identification of urine samples: a comparison between nuclear and mitochondrial DNA markers

Urine samples from 20 male volunteers of European Caucasian origin were stored at 4 degrees C over a 4-month period in order to compare the identification potential of nuclear DNA (nDNA) and mitochondrial DNA (mtDNA) markers. The amount of nDNA recovered from urines dramatically declined over time. Consequently, nDNA likelihood ratios (LRs) greater than 1,000 were obtained for 100, 70 and 55% of the urines analysed after 6, 60 and 120 days, respectively. For the mtDNA, HVI and HVII sequences were obtained for all samples tested, whatever the period considered. Nevertheless, the highest mtDNA LR of 435 was relatively low compared to its nDNA equivalent. Indeed, LRs obtained with only three nDNA loci could easily exceed this value and are quite easier to obtain. Overall, the joint use of nDNA and mtDNA markers enabled the 20 urine samples to be identified, even after the 4-month period.

A new Web site compiling forensic chromosome X research is now online

We would like to announce the opening of a new Web site ( http://www.chrx-str.org ), which contains a database surveying current research on chromosome X markers used for forensic purposes, evolutionary anthropology and other genetic research. Currently, we summarise short tandem repeat data with regard to the physical and genetic localisation, repeat structure, allele nomenclature, mutation rates and population genetics. In the future, we may include diallelic markers. The results contained in this database come from published journal articles. The authors of published articles are invited to complement their own papers by submitting data obtained from follow-up studies here. Furthermore, population data which are not able to find space in journals may be published at this Web site. The growing field of ChrX haplotyping is producing an extensive amount of data, which requires a place that can complement journal publications.

It was one of my brothers

When DNA evidence is used to implicate a suspect, it may be of interest to know whether it is likely that the suspect's near relatives also share the suspect's DNA profile. In this study we discuss methods for evaluating the probability that at least one of a set of the suspect's full or half-siblings shares the suspect's DNA profile. We present three such methods: exact calculation, estimation via Monte Carlo simulations, and estimation by means of sandwiching the probability between an upper and a lower bound. We show that, under many circumstances, this upper bound itself provides an extremely quick and accurate estimate of the probability that at least one of the relatives matches the suspect's profile.