Comparison of DNA Extraction Methods for Telogen Hair Samples

Telogen hair samples are valuable sources of DNA for forensic genetics and commonly found during crime scene investigations. The most common marker to genotype in extracts from telogen hair is mitochondrial DNA (mtDNA). With the introduction of shotgun sequencing, small, highly degraded fragments of nuclear DNA (nuDNA) from hair may be used for human identification. Here, we tested the efficacy of three DNA extraction methods designed specifically for telogen hair, and we examined and compared yields of both mtDNA and nuDNA. The methods were commonly used for isolating mtDNA in forensic genetics and ancient DNA research. Two fragments were analysed from each telogen
hair: A 2 cm fragment including the root and a 2 cm fragment immediate distal to the root fragment. The hair fragments were cleaned using an ultrasonic bath and a proteinase solution. Lysis was performed according to the published protocols. The lysis buffer contained varying amounts of Proteinase K and DTT, and the lysis incubation time ranged from 30 minutes to overnight. The extraction methods also varied in the purification step, where the techniques for isolation of DNA were based on either glass fibres or silica attached to magnetic particles or immobilised in a column. The results confirmed that both mtDNA and nuDNA is present in hair samples. The preliminary results indicated that glass fibres used for DNA isolation increased the yield of DNA, particularly nuDNA. Overall, our study provides valuable insights into DNA extraction methods for telogen hair samples, highlighting the importance of method selection based on the specific research objectives and resource availability.