The forensic DNA markers currently analysed in Germany comprise a panel of 16 short tandem repeat (STR) loci. Each consists of a stretch of tandemly arranged tetranucleotide repeat units. The individual alleles of these STR loci differ in the number of these repeat units, which corresponds to different lengths of the stretches. Nowadays these length polymorphisms are analysed using multiplex PCR of all 16 loci, the resulting amplification products being separated using capillary electrophoresis (CE).
NGS is in principle a multiplex analysis too, and the DNA sequence bears the length information as well. Therefore DNA profiles can be established using NGS, often identifying additional sequence variants within the amplicons which the current analysis ingnores. In addition, for technical reasons, in NGS analysis amplicon lengths can be kept short for all STR loci, which is not possible in CE-based analysis. Being able to analyse short DNA fragments is of tremendous advantage when analysing degraded DNA.
We have established an NGS-based protocol for the analysis of the 16 forensic STR loci and are currently successfully applying it to DNA extracted from single telogen hairs – a trace type commonly neglected due to the low amount and degraded status of its DNA. Biomedical applications of our protocol may for example consist in chimerism analysis after hematopoietic stem cell transplantation.