The Big Big Thread of Religious Discussion

[ZAKtheGeek]

Originally Posted by I_Like_Swordchucks

The main mechanism of resistance, as far as I know yet I'm only finishing up my first year in the program, is either a loss or a dysfunctional form of that particular receptor. The drug, therefore, cannot bind, giving the organism a competitive advantage in the presence of the drug. Natural selection takes it courses, and much like the moths, eventually the drug-resistant phenotype outnumbers the wild-type. So we stop using the drug. And then what happens? Those receptors have a normal physiological role, and once the environmental pressure is no longer there, the drug-resistant phenotype becomes the disadvantages organism. Eventually, the population will swing back towards the wild-type. Perfect example? Malaria was commonly treated by quinine, but then switched to more efficacious synthetic drugs after resistance developed. Now, malaria is resistance to those synthetic drugs, but is once again sensitive to quinine. Again, its not really a progressive mutation.

Well, how do you define a progressive mutation, exactly? As I understand it, evolution is basically just a response to a changing environment (assuming the organism is doing well in its "default" environment to begin with). It has no true direction or forward or backward, higher or lower. You use one drug, that drug becomes an important new part of the parasite's environment, and the species changes. You take it away, and it's another environmental change, and the species changes again. Since the new environment is similar to the original one, the trait that "gains ground" happens to be the one that was around at the time. I imagine if you were to use both drugs equally you could get it to go to a third, different trait.

...yeah, seems kinda rambling. I really hope you see what I'm trying to get at.