Inheritance, mitochondrial

The pattern of transmission of a genetic trait encoded in the mitochondrial genome. Because of the peculiarities of mitochondria, mitochondrial inheritance does not obey the classic rules of Mendelian genetics. Persons with a mitochondrial disease may be male or female but they are always related to one another in the matrilineal line. No male with a mitochondrial disease can transmit it to his children. A female with a mitochondrial disease will transmit it to all of her children. The mitochondria are normal structures or organelles in cells. They are located outside the nucleus in the cell's cytoplasm. The mitochondria are responsible for energy production. They consist of two sets of membranes, a smooth continuous outer coat and an inner membrane arranged in tubules or in folds that form plate-like double membranes (cristae). The mitochondria are in fact the principal energy source of the cell (thanks to the cytochrome enzymes of terminal electron transport and the enzymes of the citric acid cycle, fatty acid oxidation, and oxidative phosphorylation). The mitochondria convert nutrients into energy as well as doing many other specialized tasks. Each mitochondrion has a chromosome that is made of DNA but is otherwise quite different from the far better known chromosomes in the nucleus. It is much smaller and it is round (whereas the chromosomes in the nucleus are shaped like rods). There are also many copies of the mitochondrial chromosome in every cell (whereas there is normally only one set of chromosomes in the nucleus). And, since the mitochondrial chromosome is transmitted in a matrilinear manner, we have Eve to thank for our mitochondrial chromosome.