Answer to Question #98523 in Cell Biology for Abhishek

Question

COMMENT ON THE ENDOSYMBIOTIC ORIGIN OF MITOCHONDRIA .

Answer 1

According to endosymbiotic theory, mitochondrial ancestors were alpha-proteobacteria (in particular, Rickettsiales or their close relatives). А hypothetical prokaryotic anaerobic cell capable of phagocytosis captured but did not digest the aerobic heterotrophic bacterium that turned into mitochondria.

Some evidence for the theory

1. Overall similarity in shape, size, ultrastructure of mitochondrial membranes and bacteria
2. Mitochondria contain DNA other than the DNA of the cell nucleus and similar to the DNA of bacteria (ie, with a small number of nucleotides and without histone organization);
3. The formation of mitochondria in a cell is similar to binary bacterial division. Inability to form mitochondria de novo
4. Presence of own protein synthesis in mitochondria

Some evidence against the theory

1. Mitochondrial DNA is not always circular, but often has a linear shape, which is never observed in prokaryotes.
2. Features of elongation, replication, transcription and initiation in mitochondria.