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In many experiments, we can check this very easily. We can see that gene switching is not a possibility by looking at the actual DNA sequence and finding the mutation; and we can check that it is not a result of lateral gene transfer (of plasmids or anything else) by using a clonal line --- that is, you do the experiment starting with just one bacterium, yeast cell, or whatever.
That seems reasonable, however we need to be sure that the mutation is actually in a gene that codes a protein.
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In the case of the nylon-eating bacteria which Percy mentioned, the first condition holds but not the second, since this development occurred in nature and not in the laboratory. (However, one might in lieu of it consider the fact that prior to the invention of nylon, a nylon-eating bacterium would have starved to death, so common sense suggests that the development of the gene must involve a novel mutation.)
How do you know that the enzyme that nylon eating bacterium used to break down nylon wasn't formerly used for something else?
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However, there are plenty of experiments where both conditions apply --- we can identify the mutation, and we can be certain that the founder of the population didn't have it. One example would be Lenski's experiment, which you may have read about.
I could not find any info on the specific mutation that allowed these bacteria to digest citrate. How do you know it was not a mutation to a gene controller?
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Afterthought added by edit: another way we can rule out gene switching is if we can watch the process of change and know that it didn't happen immediately. If it was a pre-programmed response to environmental factors, then it would take place on introduction to the organism into the new environment, whereas if the change is a result of genuine evolution this will hardly ever be the case. So it is not always necessary to look at the gene directly.
That seems reasonable but it doesn't rule out gene switching.
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For example, when we watch the evolution of multicellularity in chlorella, not only does it not happen instantly, but we can observe several steps in the process as the first crude mutation is progressively refined to the optimal form. If this change was pre-programmed, then we'd see every organism in the experiment switch to the optimal form within the first generation, would we not? If it looks like evolution and quacks like evolution, it's probably evolution.
You mention how a crude mutation is modified to produce multicellular. This example seems like the silver bullet I am looking for. What type of genes were these mutations happening in?
I am currently exploring the evolution of decreased risk of stroke and heart disease in some people. I will try to explore your examples further but I will admit genetics is not my thing.
Apolipoprotein AI Mutations and Information
Thanks for the examples!
Edited by Admin, : Fix quote.
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