What is the “mt” in mtDNA?

Mitochondria are structures inside cells that change the energy from food into a form that cells can use. Each cell contains hundreds to thousands of mitochondria. They have their own DNA molecules that are used to create a DNA profile, called mitochondrial DNA or mtDNA. In humans, the mtDNA genome makes up only a fraction of the total DNA in cells, but it is more abundant than nuclear DNA. Most cells in our bodies contain 500 to 1000 copies of the mtDNA molecule as opposed to one or two copies of nDNA in a cell’s nucleus.

Mitochondrial DNA is maternally passed on to offspring. An mtDNA sequence analysis is an important tool for determining whether individuals are biologically related through their mothers’ side of the family. This is referred to as a maternal lineage test. The test compares the mtDNA sequences of two or more individuals. People who are biologically related will have similar mtDNA sequences, while individuals who are not will have dissimilar sequences. Law enforcement use mtDNA in finding missing persons, evidence of criminals being present at crime scenes, and the identification of Jane and John Does, including the once unknown soldiers currently under the protection of the guard at Arlington Cemetery.

 

However, although it is used after death, mtDNA also can potentially cause death. It has been proved that mitochondrial DNA is susceptible to undergo mutations that are dangerous to many living organisms. Some mutations are in the forms of cancers. Somatic (not inherited) mutations in mitochondrial DNA can increase the production of harmful molecules called reactive oxygen species. mtDNA is defenseless to the effects of these molecules and has a hard time repairing itself. As a result, reactive oxygen species easily damage the DNA, and causes a buildup of additional transformations.