Table of Contents Next Section Nontraditional Inheritance Vol. However, the existence of another genome, the mitochondrial genome, in all cells introduces another twist of biology leading to nontraditional inheritance.
Mitochondria are organelles that provide much of the energy cells use for the work they do.
Most biologists now believe that these structures evolved from microorganisms that established symbiotic relationships with the ancestors of animal cells very early in the history of life on this planet. Selection for metabolic advantages gained through symbiosis explains how it has come to be that mitochondria contain their own DNA that codes for 13 of their proteins along with ribosomal and transfer RNA that specifically help express mitochondrial series. In fact, there is evidence that mitochondrial sequences may mutate at rates 3 to 5 times greater than nuclear sequences. First, each cell contains about 100,000 mitochondria, each of which has 2 to 10 copies of its genome. Here the mixture of genotypes is termed heteroplasmy.