Animal Mitochondrial DNA and Inheritance

Animal mitochondrial DNA has its own genome, separate from nuclear DNA. It is a double-stranded, closed circular molecule with about 20,000 base pairs. One strand is the heavy, or H-strand, because it is rich in guanine. The other is the light, or L-strand, because it is rich in cytosine.

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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 bacte...