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  Topic: The Origin of "Information" via natural causes, Refuting a key ID claim (refs, webpages)< Next Oldest | Next Newest >  

Posts: 319
Joined: May 2002

(Permalink) Posted: May 20 2003,14:13   

From t.o.:

Code Sample

>> Just a couple of thoughts: another problem with Hall's selection
>> experiments on bacteria is that he's relying on existing genes to pick
>> up the function of a deleted gene. But they aren't entirely free to
>> evolve, even neutrally. Each of those proteins has a function which it
>> must maintain. A mutation that helps to replace the lost function must
>> also preserve the protein's current function, so there is the
>> possibility of selection rejecting mutations because, even if they help
>> regain the lost function, they may degrade the protein's current
>> function enough to make net selection negative. I don't know how
>> important that factor would be in practice, but it's something to
>> consider. A lot of evolution can get around this problem by beginning
>> with a gene duplication, allowing different copies to experience
>> selection in different directions.
>Yes, this is quite a problem indeed.  Gene duplication is supposed to
>get around this problem by creating sequences that can undergo neutral
>drift while maintaining previous functional sequences.  However,
>Hall's E. coli didn't do this either.  They simply didn't evolve the
>lactase function by any means, not even by gene duplication.  Neither
>have many other types of bacteria despite huge numbers of observed
>generations (over a million).

See Matsumura I, Ellington AD. In vitro evolution of
beta-glucuronidase into a beta-galactosidase proceeds through
non-specific intermediates. J Mol Biol. 2001 Jan 12;305(2):331-9)
where they have evolved a beta galactosidase that acts on lactose from
an enzyme other than the "spare tyre". I believe I have directed you
to this paper before.

  42 replies since May 30 2002,00:02 < Next Oldest | Next Newest >  

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