Mitochondria: The "Power House" of the Cell

If you visit any middle or high school biology class and ask students what cell organelle is called the "power house" of the cell, the response you should hear is the mitochondrion. If you ask students what organelle in plant cells contains chlorophyll, the response would be the chloroplast. If you ask what cell structure determines inherited traits, you would most likely hear chromosomes, genes or DNA that are in the cell's nucleus. It is interesting to note, however, that all three cell structures contain genes or DNA and exhibit their own inheritance patterns.

Mitochondrial genes are maternally inherited which means they are passed to offspring only through the mother. Sperm do not contribute any mitochondria at the time of fertilization. A woman will transfer her mitochondrial genes to all her children.

Each cell contains many mitochondria, but cells that have high energy requirements such as brain and muscle cells have many more mitochondria than other cells. Mitochondrial DNA (mtDNA) has a higher rate of mutation than nuclear DNA and is responsible for certain inherited disorders. It may also play a role in the aging process.

Mitochondrial diseases are rare and baffling genetic conditions. They can appear late or early in life, range from mild to deadly, have no known cures and few treatments.

Fatigue and degenerative changes frequently occur as one ages. These characteristics may be attributed to an accumulation of free radicals, products in the cell's energy cycle, and to changes that occur in mitochondrial DNA over one's lifetime.

Mitochondrial DNA is significant in areas other than medicine. It has been used as a forensic tool in crime investigations and in identifying the remains of soldiers. It proved conclusively that the body in outlaw Jesse James's grave is Jesse James and it was also used to solve the mystery surrounding the Romanovs, Russia's royal family.

In July 1918, the Bolsheviks executed Tsar Nicholas II, his wife, and three of their daughters. The identities were masked using sulfuric acid and the bodies were placed in a shallow grave. In 1991 the grave was discovered and suspected to be that of the Romanovs. The government began the arduous task of identifying the skeletal remains.

An individual cell contains a single nucleus but many mitochondria. Each mitochondrion contains numerous copies of its DNA and this mtDNA mutates rapidly. It is possible to see a mtDNA mutation in some mitochondria but not in others within the same cell.

This phenomenon allowed researchers to make a definitive match between the remains of two relatives in the Romanov family: Tsar Nicholas II and his brother the Grand Duke of Russia, Georgij Romanov.