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Author Topic:   Does mutation support natural selection?
LimpSpider
Member (Idle past 4263 days)
Posts: 96
Joined: 09-27-2012


Message 1 of 2 (675196)
10-08-2012 3:00 AM


Mutations are changes in the genetic sequence. Mutations are almost universally degenerative to the information encoded within the genome. Not to the organism itself.
I propose not. Here’s why (This is an analogy, of course): (The following is taken from a book called In Six Days, available free online) ...[I]magine a monkey typing on a typewriter with 27 keys, all the letters in the English alphabet and the space bar. How long would it take for the monkey to type something that made any sense? Dawkins suggests the sentence spoken by William Shakespeare’s Hamlet who, in describing a cloud, pronounces, Methinks it is like a weasel. It is not a long sentence and contains very little meaning, but it works for argument’s sake. How many attempts at typing this sentence would it take a monkey, which would presumably be hitting keys randomly, to type the sentence?
As it turns out, the odds can be easily calculated as the probability of getting each letter or space correct raised to the power of the number of positions at which they have to be correct. In this case, the probability of the monkey typing m at the first position of the sentence is 1/27 (we won’t worry about capitalization). The sentence has 28 characters in it, so the probability is (1/27)28 or 1.2 x 10—40. That is about one chance in 12,000 million million million million million million! You would want a lot of monkeys typing very fast for a long time if you ever wanted to see this happen!
...Organisms are made of cells, and those cells are composed of little protein machines that do the work of the cell. Proteins can be thought of as sentences like Methinks it is like a weasel, the difference being that proteins are made up of 20 different subunits called amino acids instead of the 27 different characters in our example. The evolution of a functional protein would presumably start out as a random series of amino acids one or two of which would be in the right position to do the function the protein is designed to do. According to Dawkins’ theory, those amino acids in the right location in the protein would be fixed by natural selection, while those that needed to be modified would continue to change until they were correct, and a functional protein was produced in relatively short order. Unfortunately, this ascribes an attribute to natural selection that even its most ardent proponents would question, the ability to select one nonfunctional protein from a pool of millions of other nonfunctional proteins.
Changing even one amino acid in a protein can alter its function dramatically. A famous example of this is the mutation that causes sickle cell anemia in humans. This disease causes a multitude of symptoms, ranging from liver failure to tower skull syndrome. It is caused by the replacement of an amino acid called glutamate, normally at position number six, with another amino acid called valine. This single change causes a massive difference in how the alpha globin subunit of hemoglobin works. The ultimate sad consequence of this seemingly insignificant mutation in the protein causes premature death in thousands of individuals each year. In other proteins, mutations to some, but not all, areas can result in a complete loss of function. This is particularly true if the protein is an enzyme, and the mutation is in its active site.
Th[e] idea of natural selection fixing amino acids as it constructs functional proteins is...unsupported by the data. Cells do not churn out large pools of random proteins on which natural selection can then act. If anything, precisely the opposite is true. Cells only produce the proteins they need to make at that time. Making other proteins, even unneeded functional ones, would be a wasteful thing for cells to do, and in many cases, could destroy the ability of the cell to function. Most cells only make about 10% of the proteins they are capable of producing. This is what makes liver cells different from those in the skin or brain. If all proteins were expressed all the time, all cells would be identical.
In reality, the problem of evolving life is much more complex than generation of a single functional protein. In fact, a single protein is just the tip of the iceberg. A living organism must have many functional proteins, all of which work together in a coordinated way
If one wishes for me to change the wording, it would not in any way change the argument. Hence I do not see that as necessary. (You may bash this as attributed to myself, and I will respond with arguments of my own (I have used this argument in various forms in other places, I don’t wish to copy from those, but copy from the original) )
Edited by Admin, : Add double spacing between paragraphs.

Replies to this message:
 Message 2 by Admin, posted 10-08-2012 9:17 AM LimpSpider has not replied

  
Admin
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Message 2 of 2 (675206)
10-08-2012 9:17 AM
Reply to: Message 1 by LimpSpider
10-08-2012 3:00 AM


LimpSpider writes:
Mutations are changes in the genetic sequence. Mutations are almost universally degenerative to the information encoded within the genome. Not to the organism itself.
I propose not...
Is this first paragraph intended as a brief statement of the current understanding of mutations' effect on information and of genomic information's effect on the organism?
And then you're saying you disagree with it?
If that's the correct interpretation then the first paragraph is not a correct statement of current understanding. I'm not taking sides, just seeking accuracy. If someone proposed a thread for Faith and Belief and stated that Christians believe Jesus Christ is Santa Claus I'd have to challenge that, too.
About the rest of your proposal, the Forum Guidelines state:
    Your proposal is predominately excerpts. Please explain your position in your own words and provide a link for reference.

    --Percy
    EvC Forum Director

    This message is a reply to:
     Message 1 by LimpSpider, posted 10-08-2012 3:00 AM LimpSpider has not replied

      
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