Mitochondrial DNA or MtDNA is DNA found in cell mitochondrial. Mitochondrial are cell organelles responsible for providing energy and are in fact called the cell’s ‘power-house’. When we talk of DNA what we normally refer to is the DNA we find in the cell nucleus and not mitochondrial DNA. Mitochondrial DNA testing finds its use in ancestry testing and genealogy; the two being closely related fields. This kind of DNA is passed through the maternal line to both males and females, but it is only females who pass it to their off spring.
MtDNA remains relatively unchanged as it is passed down through generations and although it can be used as a reliable means to determine whether people share the same maternal lineage in a relationship test or genealogical ancestry testing, it cannot tell you how close or distant the relationship is. This is because all people sharing a common maternal ancestor will also have the exact same MtDNA which they would have inherited from their common maternal ancestor. The relationship between them thus cannot be known through the DNA test. It is however, a very reliable type of DNA analysis due to the low mutation rate of mitochondrial DNA. your ancient maternal ancestry can be traced using your MtDNA. The test can tell you where your maternal ancestors came from, pin pointing the exact regions on a simplified world map.
In forensics, mitochondrial DNA is tested when victims have died under circumstances, such a fire, which might have altered nuclear DNA. MtDNA can be extracted from hair, bone and teeth and is found in relatively small quantities, especially when compared to nuclear DNA, but is as mentioned, much more resistant to being altered by environmental factors.