Narrator: This is Science Today. If your cellular metabolism is on the sluggish side don't blame Dad. Cellular organelles called mitochondria are responsible for providing the cell with the energy it needs to function, and according to Douglas Wallace, a professor of molecular medicine at the University of California, Irvine, mitochondrial genes come directly from mom.
Wallace: The mitochondrial DNA has a totally unique genetic system. Instead of having two copies per cell, one gene from the mother and one gene from the father like all the chromosomal genes, the mitochondrial DNA comes exclusively from the mother, but each cell has hundreds if not thousands of mitochondrial DNAs.
Narrator: The reason for maternal inheritance, Wallace says is that paternal mitochondria are simply outnumbered.
Wallace: Mitochondrial DNA is inherited through the cytoplasm. And since the human egg has a large cytoplasm with about 200,000 mitochondria, where as the poor little pathetic sperm has a tiny little bit of cytoplasm and only about 40 mitochondria. Mitochondrial DNA is exclusively maternally inherited.
Narrator: For Science Today, I'm Larissa Branin.