Detection of deletion/insertion polymorphism profiles from single human hair shafts

Background: Hair is a frequently encountered biological evidence in personal identification. The amount of nuclear DNA that can be extracted from a single strand of rootless hair is most limited, making the detection of short tandem repeat (STR) polymorphisms difficult. To overcome these limitations, deletion/insertion polymorphisms (DIP) as a new type of genetic marker have shown their benefits in detecting low-copy-number DNA. The Investigator DIPplex kit contains 30 biallelic autosomal DIP and amelogenin. The analysis of DIPs combines the advantages of both STR and single nucleotide polymorphism analyses. Thus, this study aimed to detect the DIP distribution of individual hair shafts from individuals. Methods and results: DNA was extracted from the shaft of fresh, aged, and shed hair. After DNA was evaluated, the DIP profiles were detected by capillary electrophoresis. The results indicated that the amount of DNA extracted from hair roots was much higher than that from the hair shafts in the same individual for all samples. The degradation index values of DNA from the aged hair shafts were highest. It is classified to be “mildly degraded.” Compared with their hair roots, the full DIP profiles were detected for fresh hair, 70% for aged hair, and 92% for shed hair. Contrarily, except for fresh hair shafts, only three STR loci of the aged and shed strands of hair could be genotyped using AmpFlSTR MiniFiler PCR Amplification Kit. Conclusions: These results indicate that the detection of DIP profile is an effective tool for personal identification from hair shafts, including aged hair.