Mitochondrial DNA (MtDNA) is a type of DNA found in the cell mitochondria. Cells are made up of a number of components and one of these cell components is the mitochondrion (plural: mitochondria). The cell mitochondria are responsible for providing our cells with the energy they need to function, they are in fact, sometimes referred to as the cell’s ‘power house’. The importance of MtDNA testing will be discussed later in this article.
When you do a paternity DNA test, a grandparentage DNA test or most other genetic tests available, the DNA you send in as sample for testing is the DNA found in the nucleus of your cells. The nucleus is the ‘control centre’ of your cells and ensures that all the cells functions run smoothly. Whilst the human cell contains only one nucleus it can contain several thousand mitochondria.
Mitochondria and our genome
Humans have 23 chromosome pairs, which mean that most of us have 46 chromosomes. Our genetic information on our chromosomes is found in the cell nucleus. Naturally, the question arises as to why we have this mitochondrial DNA which is found in a part of the cell other than the nucleus. The answer takes us back thousands of years and forms part of the evolutionary process of humans. Mitochondrial DNA contains 37 genes and some of these genes are responsible for providing the necessary proteins with the instructions for energy production.
Inheritance and you Mitochondrial DNA
What is important is the fact that only females pass this DNA to their offspring. Males do have mitochondrial DNA (they inherit it from their mother), but they do not pass it on to their children. There are several advantages MtDNA has over nuclear DNA. From an evolutionary perspective, scientists believe we have a common mitochondrial ancestor know as a “mitochondrial eve”. The advantages of testing mitochondria are the following:
- MtDNA undergoes little changes and even after death of the body, the DNA in cell mitochondria is rarely affected by environmental conditions or even destroyed by extreme heat.
- MtDNA is available in large quantities in every cell.
- MtDNA is found in places where nuclear DNA is not; for example bone fragments in parts of hair other than the root (the root is where one finds nuclear DNA).
Mitochondrial DNA testing for maternal Lineage
There are several types of relationship DNA tests available these days that can establish relationship between aunts, uncles, grandparents etc. MtDNA testing is a type of relationship DNA test. It is a great tool for tracing maternal lineage to see whether two or more individuals, be they male or female, share the same maternal line. Moreover, because MtDNA is available in large quantities per cell and is not easily degraded, even very small samples can be suitable for testing. If people share similar MtDNA then it is likely that they descend from the same maternal line.
Genealogists, anthropologists and geneticists also have great interest in MtDNA as it can help them trace ancestors accurately through maternal lines.
The test was used about a decade ago to establish whether the alleged remains of the Russian imperial family, the Romanovs, where in fact them and identified using an MtDNA test. Tsarina Alexandra, the daughter of the empress, was the granddaughter of Queen Victoria. In other words, the empress was Queen Victoria’s daughter. A living common ancestor of the queen and the Tsarina is Prince Philip who has Queen Victoria’s MtDNA. MtDNA testing of prince Philip helped establish whether the alleged tsarina’s remains where in fact the tsarina and she would have shared the same maternal line with Prince Philip and both descended from Queen Victoria.