Mitochondria
An individual's mitochondrial genes are not inherited by the same mechanism as nuclear genes. The mitochondria, and therefore the mitochondrial DNA, usually comes from the egg only. The sperm's mitochondria enter the egg, but are marked for later destruction. The egg cell contains relatively few mitochondria, but it is these mitochondria that survive and divide to populate the cells of the adult organism. Mitochondria are, therefore, in most cases inherited down the female line, known as maternal inheritance. This mode is true for all animals, and most other organisms. However, mitochondria is inherited paternally in some conifers, though not in pines or yews.