While deoxyribonucleic acid (DNA) testing has been around for a while now, recent advances in the use of mitochondrial DNA have helped forensic scientists solve crimes that involve problems in identification of individuals based on DNA evidence.

Significance

Sometimes, tissue or bodily fluid samples from a crime scene are very small, damaged or badly degraded, which makes them difficult to match to a known sample using traditional analytical techniques. Techniques for genotyping mitochondrial DNA (mtDNA) have made this process much easier.

More Abundant in the Body

The mtDNA is located in the mitochondria, which are found outside of a cell's nucleus. While human cell nuclei each contain only two copies of DNA genomes, hundreds of copies of mtDNA genomes are located outside of each cell's nucleus. This increases the chance of finding sufficient mtDNA from damaged or small samples.

Sources of Reference Samples

A person's mtDNA is inherited from his mother. So unless there is a mutation, the person's mother, siblings, as well as all other maternally related family members have identical mtDNA sequences. Therefore, comparisons of unknown and reference samples are possible using a reference sample from any maternal relative--even if the reference sample is many generations older or younger.

Function

Human mtDNA continues to play an important part in identifying victims of mass disasters, such as the Sept. 11, 2001, attack in New York City, which involve great numbers of samples with limited and degraded biological material.

Misconceptions

Unlike the television crime shows in which crime scene investigation technicians provide a DNA match seemingly minutes after receiving a sample, a 2007 National Institute of Justice report says that turnaround times in the United States vary from 30 days to as long as a year.

Source:

DNA Initiative: Mitochondrial DNA research

DNA Initiative: Compromised DNA Evidence

National Institute of Justice: Advancing Justice Through DNA Technology; March 8, 2007