Animal Mitochondrial Genetics

Mitochondria produce energy-rich ATP molecules and are the only organelles in the animal cell to have their own genetic system.  

The present-day mitochondrion is thought to have evolved from an aerobic bacterium, which formed a mutually beneficial, or symbiotic, association with its predator. 

Over time, many genes from this bacterium were transferred to the nuclear DNA of the host cell and other genes were lost, leaving behind a small but independent mitochondrial DNA.

Some cells, like muscle cells, can contain hundreds of mitochondria, while others, like red blood cells, do not contain any. Each mitochondrion can contain up to 10 copies of the mitochondrial DNA.

Mitochondrial DNA is a closed, circular molecule varying in length from 14,000 to 20,000 bps, in animal cells, as compared to millions of base pairs present in nuclear DNA. 

This mitochondrial DNA encodes only a small number of biomolecules: the 16S and 12S rRNAs, up to 25 tRNAs, and 13 respiratory chain proteins. Nuclear DNA codes for the remaining proteins required for mitochondrial function.

Around 93% of the mitochondrial DNA codes for proteins, unlike nuclear DNA, where only about 1 percent are coding regions. This