What is the main function of the michondrion?
The mitochondria are a foreign body, incorporated in a symbiotic
relationship with their host. They date from early in Earth's
evolution. They respire and generally just get on inconspicuously;
but for us, their value is that they produce ATP - an energy
necessity - much more efficiently than we can by other means. So we
think they are good for us.
You get your mitochondria from your mother. They are NOT part of
your DNA.