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Author Topic:   Irreducible Complexity, Information Loss and Barry Hall's experiments
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Message 4 of 136 (373303)
12-31-2006 11:52 PM
Reply to: Message 1 by RAZD
12-05-2006 9:46 PM

For now I will only touch on the second half of your post about the gaining of information. I would not necessarily call this a gain an information more then it is simply a rearrangement of existing information. The bacteria rearranged existing information to be able to break down lactose. I'll refer you to another paper on the Evolutionary Potential of the ebgA gene (the replacement gene for the lacZ gene which was deleted).


Interestingly, the study finds that if the lacZ gene and ebgA gene are deleted there is no chance of utilization of lactose. There is also a 35.5% sequence identity between the 2 genes as well as the proteins sharing 13 of 15 active site residues, giving credence, at least to me, that no new information has been provided rather there has simply been a rearrangement of existing information. Also, quite interesting is that the wild-type enzyme of ebgA is quite ineffective in utilizing lactose and its analog lactulose. So ineffective that these sugars cannot be utilized for growth when the operon is expressed constitutively at a level that the ebg protein constitutes 5% of the cells soluble protein (the ebgR- repressor gene was removed).

The evolutionary potential of the gene was then tested when the detla lacZ ebgR- is subject to selection on a plate of lactose. Only 2 phenotypic classes of single step spontaneous mutations were obtained, Class I and class II. Class I will grow on lactose but not on lactulose, and class II will grown on lactose but on only moderately on lactulose. No other class was found to utilize lactose or lactulose. The conclusion was that the ebg operon is quite limited in its evolutionary potential. So your example shows not only an "evolved gene" that in wild type has only feeble beta galactosidase activity towards lactose and lactulose, but also an evolved gene who's mutations to increase its activity towards lactose and lactulose, which constitutes a whopping number of 2, are hardly convincing as well.

This message is a reply to:
 Message 1 by RAZD, posted 12-05-2006 9:46 PM RAZD has responded

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 Message 5 by RAZD, posted 01-01-2007 12:44 PM jjburklo has responded

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Message 6 of 136 (373448)
01-01-2007 2:50 PM
Reply to: Message 5 by RAZD
01-01-2007 12:44 PM

Re: A > B and C = A therefore C > B
First, you are comparing and old mechanism that has undergone thousands of years of evolution and natural selection to continually become more robust and capable to one that is only a few years old and has only passed ONE mutation and selection event.

No, I'm comparing a known system(which in my opinion did not evolve) that utilizes lactose and lactulose with a system that in the words of those that composed the study provides an "evolutionary constraint" to the utilization of lactose and lactulose in the absence of the lacZ gene under their particular solution and under their experimental conditions. My point is simply that your example is hardly concrete. I would divulge deeper into this but its the New Years and I'm going to spend the rest of it with my family. Happy New Year to you and thanks for the debate.

Edited by jjburklo, : No reason given.

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