PhD defence A.F. (Arwin) Ralf

Summary:

Y-STRs are short repetitive DNA motifs located on the human Y chromosome. These regions of the DNA are particularly useful in forensic genetics, especially in sexual assault cases where the traces contain an excess of female DNA and only a small amount of male DNA. Female DNA does not contain a Y chromosome, which means that even in such mixtures, a profile can be made using Y-STRs that can be fully attributed to the male perpetrator. However, there is a problem: the Y chromosome between relatives related in the male line is nearly identical, so for example fathers and their sons, or brothers will usually display an identical Y-STR profile. To link suspects to a crime, there is a need for a unique DNA profile. In this thesis I searched for new so-called rapidly mutating Y-STRs (RM Y-STRs), specific Y-STRs that mutate very often. Due to the higher mutation rate, there is an increased chance that close relatives can be distinguished from each other and a very high chance that distant relatives produce different profiles. In this thesis I also developed a method to efficiently analyze these RM Y-STRs, called RMplex, which was then applied to large numbers of relates males to empirically determine the effectiveness of the method to produce distinguishing Y-STR profiles. Additionally, the results show that RMplex could be highly useful for detecting unknown perpetrators (men whose DNA profiles are not yet included in the DNA database for criminal cases) through kinship research.