STR data for the AmpFlSTR Identifiler loci from Swedish population in comparison to European, as well as with non-European population.

The modern Swedish population is a mixture of people that originate from different parts of the world. This is also the truth for the clients participating in the paternity cases investigated at the department. Calculations based on a Swedish frequency database only, could give us overestimated figures of probability and power of exclusion in cases including clients with a genetic background other than Swedish. Here, we describe allele frequencies regarding the markers in the Identifiler-kit. We have compared three sets of population samples; Swedish, European and non-European to investigate how these three groups of population samples differ. Also, all three population sets were compared to data reported from other European and non-European populations. Swedish allele frequencies for the 15 autosomal STRs included in the Identifiler kit were obtained from unrelated blood donors with Swedish names. The European and non-European frequencies were based on DNA-profiles of alleged fathers from our paternity cases in 2005 and 2006.

Identification of mammal species using species-specific DNA pyrosequencing.

In forensic casework it is highly relevant to be able to deduce the species origin of an unknown biological sample. For such a purpose we have designed and developed an assay for species identification based on DNA sequencing of two short mitochondrial DNA amplicons. In short, partial 12S rRNA and partial 16S rRNA fragments (approximately 100bp) are amplified by PCR followed by direct sequencing using pyrosequencing technique. Due to properties of the chosen targets, the same PCR conditions and primers were used irrespective of the true species of an unknown sample. A total of 28 different mammals present in the European fauna were sequenced both for the partial 12S rRNA and the partial 16S rRNA sequences for accuracy verification. Together the two sequences showed to have a high divergence factor, discriminating almost all mammals. Furthermore, the human reference nucleotide sequences were always at least nine nucleotides different compared to the other sequenced species both at the partial 12S rRNA and the partial 16S rRNA sequences.

DNA-testing for immigration cases: the risk of erroneous conclusions.

Making the correct decision based on results from DNA analyses and other information in family reunification cases can be complicated for a number of reasons. These include stratified populations, cultural differences in family constellations, families with different population origin, and complicated family relations giving complex pedigrees. The aim of this study was to analyze the risk of erroneous conclusions in immigration cases and to propose alternative procedures to current methods to reduce the risk of making such errors. A simulation model was used to study different issues. For simplicity, we focus on cases which can be formulated as questions about paternity. We present an overview of error rates (of falsely included men as the true father and of falsely excluded true fathers) for fairly standard computations, and we show how these are affected by different factors. For example, adding more DNA markers to a case will decrease the error rates, as will the inclusion of more children. We found that using inappropriate population frequency databases had just minor effects on the error rates, but the likelihood ratios varied from an underestimation of 100 times up to an overestimation of 100,000 times. To reduce the risk of falsely including a man related to the true father we propose a more refined prior including five hypotheses instead of the two normally used. Simulations showed that this method gave reduced error rates compared with standard computations, even when the prior does not exactly correspond to reality.

Y-chromosome diversity in Sweden - a long-time perspective.

Sixteen Y-chromosomal binary markers and nine Y-chromosome short tandem repeats were analyzed in a total of 383 unrelated males from seven different Swedish regions, one Finnish region and a Swedish Saami population in order to address questions about the origin and genetic structure of the present day population in Sweden. Haplogroup I1a* was found to be the most common haplogroup in Sweden and accounted, together with haplogroups R1b3, R1a1 and N3, for over 80% of the male lineages. Within Sweden, a minor stratification was found in which the northern region Västerbotten differed significantly (P < 0.05) from the other Swedish regions. A flow of N3 chromosomes into Västerbotten mainly from Saami and Finnish populations could be one explanation for this stratification. However, the demographic history of Västerbotten involving a significant male absence during the 17th Century may also have had a large impact. Immigration of young men from elsewhere to Värmland at the same time, can be responsible for a similar deviation with I1a* haplotypes. Y chromosomes within haplogroup R1b3 were found to have the highest STR variation among all haplogroups and could thus be considered to be one of the earliest major male lineages present in Sweden. Regional haplotype variation, within R1b3, also showed a difference between two regions in the south of Sweden. This can also be traced from historical time and is visible in archaeological material. Overall this Y chromosome study provides interesting information about the genetic patterns and demographic events in the Swedish population.