The Motley Fool Discussion Boards

Previous Page

Religion & Culture / Creation vs. Evolution


Subject:  Re: Irreducible Complexity Date:  5/24/2001  8:54 PM
Author:  coolerthanranch Number:  1344 of 26642

Behe said that IC is falsifiable, well it has already been falsified

Here's just one example

How about the "Lac" genes in bacteria. Lactose is a double-sugar that bacteria can use as food. But to do so the bacteria have to produce an enzyme that can cut lactose up into its two constituent sugars, glucose and galactose. The enzyme that does this is called galactosidase. Bacteria are pretty smart, because they do not produce galactosidase when there is no lactose on their environment. The galactosidase genes automatically shut off when no lactose is present.

The bacteria are able to keep the galactosidase genes turned off by means of a control gene that only allows the genes to be expressed in the presence of lactose. A group of scientists deleted the gene for galactosidase in a culture of bacteria.(7) They then grew the culture in a medium of lactose. Of course, because they lacked the ability to produce galactosidase, the altered bacteria and their offspring could not use lactose for food - at first. But before long, mutant strains appeared that could digest and use the lactose almost as well as the original strains.

What happened? How could mutations randomly reproduce the galactosidase gene so quickly? They didn't! The mutant bacteria did not make new galactosidase . Nature simply tinkered with another gene. A new mutation in an existing gene made its protein capable of breaking apart the lactose sugar. But the bacteria didn't stop there. The researchers looked at the control genes for the new gene that cleaved the lactose. They had become modified too, and some of them responded directly to lactose, switching the gene on and off as needed.

That is not all. The researchers continued to grow the mutant cultures that could utilize lactose. But they grew some on lactulose, a different sugar, and a new mutant strain appeared that could produce allolactose, the same chemical that bacteria normally use to turn on their "Lac" genes. This is significant because now the "Lac" genes could switch on the gene for Lac permease, which is an enzyme that speeds the entry of lactose into the cell. (In the original strain of bacteria the presence of galactosidase turned on this gene for allolactose, but the mutated stains did not produce galactosidase so the Lac gene for Lac permease could not be turned on - until this new mutation.) When the Lac permease gene now gets turned the increased lactose flow into the bacterium causes the control genes for the new lactose cleaving gene to activate. The system is now irreducibly complex.

Look at the complexity of this system. Lactose triggers a sequence that turns on the new lactose-cleaving gene. The enzymes produced by the gene metabolize the lactose. The products of the lactose metabolism then activate the gene for Lac permease, which ensures a steady supply of lactose entering the cell. A completely irreducibly complex system. One part is no good without the other. Each dependent upon the other. But the system evolved in a lab!

Copyright 1996-2018 trademark and the "Fool" logo is a trademark of The Motley Fool, Inc. Contact Us