From: seanpitnos...@naturalselection.0catch.com (Sean Pitman)
Date: Tue, 21 Oct 2003 12:13:27 +0000 (UTC)
Local: Tues, Oct 21 2003 8:13 am
Subject: Re: The Density of Beneficial Functions
drear...@hotmail.com (Von Smith) wrote in message <news:email@example.com>...PDF link:
> > Yes, this is the question. Please then Ian, explain to me why ebg
> > negative E. coli cannot go from anything that they have in their
> > collective genomes in a large colony with over 4 million base pairs
> > each, to the lactase function? - if this lactase function is truly
> > only one step away from some other beneficial sequence or series of
> > one-step beneficial sequences in these creature's DNA? Hmmmmmmm?
> > That *is* the question!
> The answer is that the premise of the question isn't true. When are
> Matsumura I, Ellington AD. In vitro evolution of
If you had read this paper yourself, you may have noticed several
What is especially interesting here is that this potential lactase
> It has been cited to you several times.This is the first time I've seen it. I don't read everything that is
addressed to me in this forum you know . . .
> I don't think Matsumura etThe reason why Matsumura did not need to knock out the ebg gene was
> al. made any point in knocking out the ebg gene to get this function,
> but there is no reason to suppose they couldn't have.
that this study was an "in vitro" study, not an "in vivo" study. The
mutations were introduced into the wild-type gusA "via mutagenic PCR".
> So there are, in fact, at least *two* other genes that have beenMost likely there are trillions of potential lactase genes out there
> observed to evolve novel lactase function in E. coli in the lab. How
> many more do you think we need to observe?
in sequence space. A demonstration of two of them is nothing. The
ratio of beneficial sequences vs. non-beneficial sequences is the
issue here. What is the density of beneficial sequences in sequence
space *at a given level of functional complexity*? A lower levels of
functional complexity, such as the level of antibiotic resistance
and the like, the beneficial density of sequences is relatively high.
At the higher level of single protein functions the density of
beneficial functions becomes much much less. This is evident from the
fact that the evolution of single protein enzymes is much harder to
achieve than the evolution of antibiotic resistance in these same
bacteria. Even those bacteria that cannot evolve the lactase function
are easily able to evolve antibiotic resistance to all kinds of
different antibiotics. Moving up one more level to multi-protein
functions were all the proteins work together at the same time in a
specific orientation with each other, there simply are no examples of
evolution in action - period. Now, why is that?
> Von SmithSean
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