The geographic origin of the cell-donor

Although the current use of human DNA for forensic analysis (“DNA profiling”) usually provides high probabilities for individual identification, this is only true if the person to be identified is known to the police already. In contrast, the current methods can not aid in identifying a completely unknown person. Hence, if standard policing cannot find the right suspect, or if the offender's DNA profile is not already included in the criminal DNA databases, it is likely that the case will not be solved. Besides increasing the size of the criminal DNA database (which is a societal and political decision) one way to trace unknown persons would be to extract more information from the crime scene sample, which can lead police investigation towards finding the right suspect. One such aspect is knowledge about the bio-geographic origin (or genetic ancestry) of an unknown person; in other words from which geographic region of the world a person and its ancestors come from.

In this research line we perform systematic scans of the entire human genome (using SNP chips) of worldwide human populations and apply statistical methods to find DNA markers that contain the maximum amount of information about the geographic origin of a person (so called ancestry-sensitive markers, ASMs). We then test the performance of these ASMs in independent population samples to verify their reliability. We have shown recently that sets of small to medium numbers of ASMs can be developed for reliable identification of continental ancestry i.e. if someone originates from Africa, Asia, Europe or the Americas, including mixed ancestry from these regions. We also showed recently that with hundreds of thousands of random DNA markers, European ancestry can be further defined  towards 
sub-regions (such as North, South, West, or East Europe). Furthermore, we and others have previously generated enormous knowledge about the worldwide distribution of paternally-inherited
(Y-chromosome, YHRD) and maternally-inherited (mitochondrial) DNA (EMPOP), which revealed numerous ASMs for continental as well as regional inferences. The goal of this research line is to develop robust sets of ASMs from Y-chromosomal, mitochondrial and autosomal parts of the human genome for the reliable identification of bio-geographic origin on the continental as well as regional level of resolution also allowing quantifying mixed ancestry. As we aim to apply such ASM marker sets to forensic casework at the end, the genotyping methods we are developing need to take into account the specific requirements of forensic DNA analysis (high sensitivity, multiplexing etc.).