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Are selected for mutations simply random occurences?

  1. Jul 12, 2007 #1
    Are "selected for" mutations simply random occurences?

    I just read Carl Sagan's and Ann Druyan's Shadows of Forgotten Ancestors and there is something that I am not fully clear about. I will give an example:

    Let us suppose that there is a zebra-like creature. Over time, the zebra-like creature evolves into a mammal that is much harder for predators to detect; it loses its contrasting black and white stripes and takes on a tanish color, letting it camoflauge easier in the African savanah.

    How did this tanish color evolve? Was it simply a completely random mutation that one or two animals were born with, passing the mutation on to future generations and having the mutation being "selected for" throughout the species because many other of these creatures simply die due to being easy prey, thus being unable to pass THEIR genes on? Or does something in the DNA say "Look, we need to develop a new survival strategy"? I tend to think that it is the former, as the latter does not make much sense to me, but I just want to be sure.

  2. jcsd
  3. Jul 12, 2007 #2


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    The mutation is random, but the selection is not, the selection is "natural", i.e., preferred by the environment such that it will be of aid to the organism long enough that it has an advantage until it breeds.
  4. Jul 12, 2007 #3


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    There is one exception to that: human intervention. Many survival traits such as frost resistance in tomatoes are deliberately engineered these days.
  5. Jul 16, 2007 #4


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    Too bad they didn't have GModification for humans during WWII. My uncle lost all his toes to frost bite after crashing his bomber in Greenland and waiting for rescue.:rolleyes: (Actually I think he'd rather have no toes than the genes of an Artic krill to pass on to his descendents. :wink:
  6. Jul 22, 2007 #5
    In most cases it is the random mutation - directed selection process.

    But... Imagine that the selection is not between genes that decide the colour of the stripes but mutations and selection of genes controlling the rate of - controlling and repair of mutations. Or the meiosis process. In other words - genes that control the mechanisms of replication.
    In such cases it may be that the selection process may affect the mutation. The very fact that cells do contain mechanisms for repairing the `easy errors' of DNA replication is a proof that not everything is random.

    I recommend old, but very illuminating Extended Phenotype by Richard Dawkins.
    Last edited by a moderator: Jul 22, 2007
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