I thought I remembered discussion from ~25 years ago that the main reason for the maintenance of
mitochondrial genomes were that the proteins encoded by mtDNA were extremely hydrophobic. Under this
hypothesis, they had minimal chances of crossing the cytoplasm and multiple membrances. mtDNA ensured that
the proteins were made at the site they were needed.
David Mathog wrote:
> In article <8pr430$s9c$1 at mercury.hgmp.mrc.ac.uk>, Dr. Ram Samudrala <ram.samudrala at stanford.edu> writes:
> >I would turn that around and ask: why do you think they should go to
> >the nucleus? It seems a system that works well initially evolved this
> >way---what selective advantage do you see to those genes being in the
> >nucleus as opposed to being in the mitochondrion.
>> Advantages: Recombination and diploidy (or higher). The genes of the
> organelle needn't be perfectly adapted at all times - think about what
> happens when one suffers a deleterious mutation. Sex is good for the
> genes, but organelles don't have sex, only cells containing organelles do.
>> I also suspect that the repair of DNA mutations is much better for nuclear
> genes. Although that probably was't true the day the first organelle
> crawled into the cytoplasm, the first two factors would lead to nuclear
> migration of genes, and that would tend to break the DNA repair systems in
> the organelle.
>> David Mathog
>mathog at seqaxp.bio.caltech.edu> Manager, sequence analysis facility, biology division, Caltech