When we discuss DNA and inheritance, we are generally talking about nuclear DNA, half of which is provided by each parent. But there is also a small amount of mitochondrial DNA in each cell, 37 genes worth, that, in the great majority of species, is inherited purely from the mother. Since this DNA has a predicatable rate of mutation, genetic scientists have been able to use mitochondrial DNA to study the sequence of evolution and species dispersal patterns throughout the history of our planet.
Mitochondria are small organelles within the cytoplasm of our cells that are important in energy production and protein assembly. It is thought that they originated in the early stages of life's history on Earth, when bacteria became incorporated into other single-celled organisms; this likely occured before nucleated cells evolved. In animals that reproduce through sexual mechanisms, only the mitochondria of the egg are preserved; those of the sperm are destroyed during the process of fertilization.
So, on this Mother's Day, when you thank mom for all that she has done, don't forget to mention that mitochondrial DNA. You couldn't live without it!
