Persistence of separate mitochondrial genome

Dr.Ram Samudrala ram.samudrala at stanford.edu
Thu Sep 14 02:42:42 EST 2000


Andrew Gyles <acgyles at my-deja.com> wrote:

>At a conference in Italy in 1994 Saccone et al said, 'The fundamental
>question..."why mtDNA and a separated organellar genetic system should
>have persisted throughout evolution?" is still waiting for a convincing
>answer'(1).

>Has any progress been made in answering this question since then? The
>authors also said, 'Another intriguing question is why evolutionary
>process(es) led to the extant scenario: a genome with a reduced, but
>often similar information content in almost all organisms in spite of a
>great variation in size'.

>To be more specific, I would ask why have the genes coding for
>respiratory enzymes remained in the mitochondrion in most cases
>instead of going to the nucleus?

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.  

If there is no significant selective advantage or disadvantage, then
perhaps the events that would result in those genes being incorporated
into the organismal DNA haven't occured yet.

--Ram

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