Evolutionary outsourcing

It is believed that mitochondrion was once a free living bacteria. As multi-cellular life forms evolved they simply used the mitochondrion as the energy house - the simplest form of what is called outsourcing today. Biologists would term them symbiotic relations. Over time, this symbiotic behaviour has become an integral part of a cell evolving in its own way.

Mitochondrion have their own DNA, a circular DNA like most bacteria. They divide by simple mitosis. However it is also strange that mitochondria not only grow and divide, but can also combine into another mitochondrion. Also unique is the manner in which mitochondria is passed genetically. During fertilisation the mitochondrial DNA comes only from the egg and hence used to study maternal lineage.

I guess if we had recombinant DNA, the mitochondrion may once again become a free living bacteria (with its own free will) which is probably why the evolutionary contract specifies capital punishment for the male mitochondrion!