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Specific Melanin Content in Human Hairs and Mitochondrial DNA Typing Success

Linch, Charles A. BS*; Champagne, Jarrod R. BS†; Bonnette, Michelle D. BS†; Dawson Cruz, Tracey PhD†‡

American Journal of Forensic Medicine & Pathology: June 2009 - Volume 30 - Issue 2 - pp 162-166
doi: 10.1097/PAF.0b013e3181873c69
Original Article

This study investigated whether a difference exists in the ability to obtain quality mitochondrial DNA (mtDNA) sequence data from hair shafts due to specific melanin content differences. Eumelanin, the pigment in darker hairs, protects nuclear DNA in the skin by absorbing and scattering UV radiation. In contrast, sensitized pheomelanin, the predominate melanin in red hairs and some blond hairs, is unable to prevent DNA damage in skin upon exposure to UV radiation. It has been reported in the literature that darker hairs (predominate eumelanin content) have a higher mtDNA sequencing success rate than lighter colored hairs. However, others have reported to the contrary when different methodologies are used. In this study, 2-cm hair fragments were cut from dark brown, red, and gray white hairs and typed using standard casework mtDNA sequence analysis methods. All 30 hair fragments produced quality mtDNA sequence data on first attempt from the second half of hypervariable region 1. These results are likely due to the apparent shielding of mtDNA by the hard protein of the hair shaft fiber from radiation-induced damage, regardless of melanin type, after 10-months minimal solar exposure. Nonetheless, this study may serve as a guide for future quantitative studies that investigate hair mtDNA photodamage in circumstances of increased solar, chemical, environmental, or mechanical damage.

From the *Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX; and Departments of †Forensic Science and ‡Biology, Virginia Commonwealth University, Richmond, VA.

Manuscript received April 3, 2007; accepted December 6, 2007.

Supported by grants from the offices of the Provost and the Dean of the College of Humanities and Sciences at Virginia Commonwealth University.

Reprints: Tracey Dawson Cruz, PhD, Departments of Forensic Science and Biology, Virginia Commonwealth University, 1000 W. Cary St, PO Box 842012, Richmond, VA 23284. E-mail: tcdawson@vcu.edu.

© 2009 Lippincott Williams & Wilkins, Inc.