Several questions on evolution, and mutation (rate)

Ram Samudrala ram at mbisgi.umd.edu
Fri Sep 6 19:45:24 EST 1996


James Foster (foster at cs.uidaho.edu) wrote:

>Ahhh...gotcha.  That is indeed an interesting question.  I'm not sure
>what the answer is.  I know that many new functions are co-opted from
>similar functions (I think the classical example is some enzyme
>beginning with the letter l...but can't remember right now).  But that
>begs the question of where the co-opted behaviors came from.

True, and I think also the important issue is how this new function
arose from a similar function.  The evolution, and natural selection,
of classes of beta-lactamases are the examples I know.  While we
haven't observed it, the early beta-lactamases are hypothesised to
have arisen from cell-wall enzymes and the bacteria were facing an
enemy in nature (beta-lactams in fungi).  Today, we have artificial
beta-lactams that are not seen anywhere in nature, yet there are
bacteria resistant to it.  One explanation that this new function
/arose/ (evolved) in the the last few decades, compared to the initial
ones, which might've been around for thousands of years and then were
selected for when we first developed beta-lactams?  Or maybe the
genes were already present for all classes of beta-lactams?

I think natural selection is a very strong theory.  Evolution, on the
other hand, poses interesting questions (like the ones above).

On further thoughts, I think there are two definitions of evolution
(at least).  Evolution, as a subject, refers to the entire process:
arising of function, and natural selection.  That is, how a species
evolves over time.   Evolution can also simply refer to the arising of
new function.

>I have seen the new evidence supporting some Lamarkian mechanism, so
>your last question does merit some investigation.

Yes, there're some papers in Nature about adaptive mutation I read a
while ago. 

Also, relevant to this is the mechanism of antibody formation.  That's
basically evolution and natural selection in our bodies.

--Ram

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