At 01:53 PM 9/27/98 -0400, Tim Ikeda wrote:
>Hello Glenn,
>You wrote:
>[...]
>] Perrot allowed laboratory cutlures of E. coli with rpsL mutations to
>] evolve in an antibiotic-free medium for 16 days or 160 generations.
>] They then completed these evolved bacteria against drug-sensitive E.
>] coli and found that they are almost as fit. 'That suggests that they
>] evovled a compensatory mutation,' says Levin-a second genetic mutation
>] that makes up for the loss of fitness from the first.
>] "Schrage and Perrot, with Levin and Nina Walker, confirmed that suspicion
>] by making their evolved E. coli strain drug-sensitive again. They
>] replaced the bacteria's streptomycin-resistant rpsL gene with a sensitive
>] version of the gene, then set this genetically altered strain and the
>] resistant strain against each other ina another fitness-competition bout.
>] The genetically altered E. coli failed miserably-implying that the
>] compensatory mutation reduced its fitness when not paired with the
>] resistance gene.
>[...]
>
>Good heavens, yet another "irreducibly complex" system arises! Did the
>researchers happen to notice a big guy with a white beard (not Santa)
>hanging around their lab during the experiments? Were they able
>to rule out extranatural assembly as the source of the compensatory
>mutations or did someone who was supposed to monitor the incubator
>fall asleep one night?
You know, sometimes you read something and just miss a very important item.
I really hadn't noticed that this represents the evolution (within the past
50 years) of an 'irreducibly complex' system -- antibiotic resistance and a
compensating mutation. Here indeed is an example that clearly demonstrates
that irreducible systems can arise by normal mutation and selection.
Thanks for calling my attention to this. Can't understand why I didn't see
it before.
glenn
Adam, Apes and Anthropology
Foundation, Fall and Flood
& lots of creation/evolution information
http://www.isource.net/~grmorton/dmd.htm