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!
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Shamit's question: What is the mitochondrion's benefit in the symbiotic relation?
ReplyDeleteThis would entail a post in itself, but a simple answer would be roti, kapda aur makan. It derives its food from the cell and at the same time protected from the external environment - though I'm not sure what predators confront bacteria, but at least it does not have to face the wrath of nature!
well put :) just a couple of comments, genetic recombination will only put IN the mitochondria into the genome,it will be even less f a freeliver :) however as ananth has pointed out, yes, it makes its own protein synthesis machinery and infact has rather cool deviations from that of its 'houser' that help it get by with fewer genes. So one would think that with not too much trouble it should be able to break the shackles! :)
ReplyDeleteseconldy, because of its mode of inheritance, the elephant lineages in mudhumalai have been very neatly mapped out using dung samples from existing elephants and checking for specific changes in the mitochondrial DNA, which must have come from one parent only, and so can be traced back easily. Interestingly elephants live in mtariarchal societies :) with the mother and aunts ruling!