Mitochondria and inheritance
All your body's cells contain mitochondria, tiny sausage-shaped 'powerhouses'. Mitochondria have their own small amount of DNA, which make proteins needed to generate energy for the cell. All your mitochondria are copies of the 100,000 that were inside your mother's egg cell, which went on to make you. Your father's sperm also contained mitochondria but they were lost after his sperm entered the egg. So mitochondria are passed from a mother to her sons and daughters, but only her daughters pass them on to their children.