What is mitochondrial DNA?

Mitochondrial DNA (mtDNA) is the DNA found inside the Mitochondria organelle. This organelle produces energy in our cells to carry out cellular functions. The mtDNA contains approx 16,500 base pairs and is unique to an individual. This property is what makes mtDNA very useful in forensic science. The mtDNA is usually used when nuclear DNA is too damaged or degraded to use for DNA tests.

What makes mtDNA so special and how does it help with forensic DNA testing?

• Identical copies– the mtDNA is very conservative, which means although it undergoes recombination, it does not change and combines to create identical copies of itself. But this feature comes with a disadvantage, which is the risk of mutation in the mitochondrial DNA. That is, the risk of the mutations occurring in this DNA is 10 times higher than that of nuclear DNA.
• Easy availability– there are about 2000 mitochondria that are present in each human cell. That means obtaining samples of mitochondrial DNA is much easier than nuclear DNA. This is where forensic science takes advantage of mtDNA. In cases where the forensic scientist has to usually work with bones, teeth, and hair, the mitochondrial DNA can be obtained easily.
• Maternally inherited– since mtDNA is maternally inherited without many changes in the sequence, it is used in many kinds of forensic cases. For example, cold cases have been solved using small pieces of biological evidence that were found at a crime scene.

Some other uses include the identification of a missing individual based on mtDNA inherited by that individual. This can be done by obtaining the mtDNA sample of the person and comparing it with the samples of the relatives. Since the same mitochondrial DNA is inherited by different individuals, biological relativity can be determined by forensic DNA testing.