Mammalian mitochondrial DNA (mtDNA) is a small 16.5 kbp circular genome. Human mtDNA was found to contain two adjacent, highly polymorphic regions, which are designated hypervariable regions I and II (HV-I and HV-II). The most common polymorphisms are nucleotide substitutions (transitions and transversions) followed by deletions and insertions (Butler and Levin, 1998; Meyer et al., 1999). Polymerase chain reaction (PCR)-amplification and subsequent sequencing of these two polymorphic regions is currently referred to as 'mtDNA typing' and the sequences obtained by this technique as 'mtDNA types' (Holland and Parsons, 1999; Carracedo et al., 2000).

Short tandem repeat (STR) typing, an established forensic typing method based upon nuclear DNA (nDNA) polymorphisms, is highly effective when DNA is of sufficient amount and quality (Moretti et al., 2001). Frequently, due to inadequate quantity or degradation of the sample into small fragments, DNA extracted from forensic samples is of limited use. Samples notorious for unsuccessful STR typing include old bones, teeth and hair, particularly hair that has been shed, as these samples generally lack detectable nDNA. Even blood and body fluid samples, which are frequently used for STR typing, occasionally give unsuccessful results due to sample aging or decomposition. For these types of samples, mtDNA typing has proven to be more successful than STR typing, though the individual discrimination power of mtDNA typing is in general lower than with STR typing.

Molecular Forensics. Edited by Ralph Rapley and David Whitehouse Copyright 2007 by John Wiley & Sons, Ltd.

This chapter describes the relevance of mtDNA biology to forensics, mtDNA typing and two additional topics of forensic interest: species identification through mtDNA analysis and the attempt to increase individual discrimination power by typing single nucleotide polymorphisms (SNPs). Detailed reviews of mtDNA forensic applications can be found in Butler and Levin (1998), Holland and Parsons (1999) and Budowle et al., (2003).

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