Special Considerations For Hair Evidence

Hair and fiber examiners can perform microscopic comparisons of hairs much more quickly than mtDNA can be analyzed and therefore can be used as an effective screening tool to reduce the amount of evidence processed through the steps of mtDNA sequencing. A correlation of microscopic and mitochondrial DNA hair comparisons found that the techniques can be complementary (Houck and Budowle 2002).

With hair evidence, the physical examination by a hair examiner must be performed prior to the mtDNA testing as the hair is destroyed during the extraction process. Typically for analysis of hair shafts, a tissue grinder is used to break down the keratin structure of the hair and release the mtDNA molecules (Wilson et al. 1995a). Usually 1-2 cm of hair shaft is ground up after carefully cleaning the outside of the hair (Jehaes et al. 1998).

Comparisons of head, pubic, and axillary hair shafts found the highest success rate with head hair shafts (Pfeiffer et al. 1999). The addition of bovine serum albumin or BSA (Giambernardi et al. 1998) helped reduce the PCR inhibitory effects of melanin previously noted by Yoshii et al. (1992) and Wilson et al. (1995a). A nested PCR amplification approach has successfully recovered mtDNA sequence information from as little as 33-330 femtograms of genomic DNA, which is equivalent to 10-100 copies of mtDNA (Allen et al. 1998).

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