Sensitive Identification Tools in Forensic DNA Analysis

Abstract: DNA as forensic evidence is valuable in criminal investigations. Implementation of new, sensitive and fast technologies is an important part of forensic genetic research. This thesis aims to evaluate new sensitive methods to apply in forensic DNA analysis including analysis of old skeletal remains.In Paper I and II, two novel systems for analysis of STRs, based on the Pyrosequencing technology, are presented. In Paper I, Y chromosomal STRs are analysed. Markers on the male specific Y chromosome are especially useful in analysis of DNA mixtures. In Paper II, ten autosomal STRs are genotyped. The systems are based on sequencing of STR loci instead of size determination of STR fragments as in routine analysis. This provides a higher resolution since sequence variants within the repeats can be detected. Determination of alleles is based on a termination recognition base. This is the base in the template strand that is excluded from the dispensation order in the sequencing of the complementary strand and therefore terminates the reaction. Furthermore, skeletal remains are often difficult to analyse, due to damaging effects from the surrounding environment on the DNA and the high risk of exogenous contamination. Analysis of mitochondrial DNA is useful on degraded samples and in Paper III, mtDNA analysis of 700 years old skeletal remains is performed to investigate a maternal relationship. The quantity and quality of DNA are essential in forensic genetics. In Paper IV the efficiency of DNA isolation is investigated. Soaking skeletal remains in bleach is efficient for decontamination but result in a lower DNA yield, especially on pulverised skull samples.In conclusion, this thesis presents novel sequencing systems for accurate and fast analysis of STR loci that can be useful in evaluation of new loci and database assembly as well as the utility of mtDNA in forensic genetics.