Mitochondrial DNA

Mitochondrial DNA

Mitochondria are structures within cells that take the energy from food and develop it into a form useful for the cells. Unlike chromosomes, both autosomes and allosomes, which are within the nucleus of a cell, Mitochondria are outwith the nucleus, as separate structures within the cell. Both eggs and sperm have mitochondria in them, but the mitochondria in the sperm are in its tail which does not enter the egg during reproduction – therefore children only receive mitochondrial DNA from their mother.

Mitochondrial DNA spans around sixteen thousand base–pairs and contains thirty–seven genes. All of the genes in mitochondrial DNA are concerned with normal mitochondrial function. For example, providing instructions for making enzymes involved in oxidative phosphorylation – using oxygen and simple sugars to create ATP (adenosine triphosphate), the cell's main energy source.

Mitochondrial DNA is being used by military laboratories to identify skeletons discovered in old war zones – WWII, Vietnam and Korea – by tracing the mtDNA to living relatives.

Why not the X?

As we use the Y Chromosome to trace the fatherline, you may be wondering why we do not use the X Chromosome to trace the motherline. Yes, the X Chromosome in a male comes from his mother, but in a female, they get an X Chromosome from each of their parents, and it is a 50% chance which X Chromosome they pass on to their child. This would not, therefore trace the motherline’s ancestral origins, as parts of the X Chromosome may have come from your mother’s father, and even if not, certainly some parts of will have come from another male ancestor somewhere down the line. The X chromosome DNA is also shuffled each generation and so we cannot easily trace which ancestor the DNA came from, and cannot build a tree relating different types.

Mitochondrial DNA is passed from a mother to all of her children, but only daughters then pass it on. Like the Y Chromosome, mitochondrial DNA is also inherited as one block and contains many markers that allow us to identify over one hundred different groups of related lineages and many subtypes within each group. mitochondrial DNA is very interesting, as women often left their places of birth to find partners. Your mitochondrial DNA may have originated on the other side of the world.