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Evolution and Mutation

  1. Sep 19, 2006 #1
    As Ive learned it, mutations can be grouped into 3 categories as they relate to evolution: harmful, neutral, or beneficial. Is there any way to figure out the ratios (in relation to each other) of these types of mutations?
     
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  3. Sep 19, 2006 #2

    selfAdjoint

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    Some mutations are obviously harmful of course - gross teratologies, or offspring born dead - but in evolutionary terms benefit or harm can only be determined long after the fact, by the number of phenotype descendents reproducing the mutated gene.

    Let me cite an example of how it's not simple. Speed is a great advantage to cheetahs in hunting for food, so they have evolved under strong selective pressure to emphasize speed. It happens that cheetah speed is a single strong feature of the cheetah genome.This has resulted in the whole population of cheetahs being nearly as identical to each other genetically as twins or clones. And that has put the whole population of cheetahs in great peril, because any slight genetic flaw or mutated virus could knock every one of them out if it could knock any one out. By contrast humanity can survive plagues (like the medieval Black Death) because of rich genetic variety.
     
    Last edited: Sep 19, 2006
  4. Sep 19, 2006 #3
    There is no "one" ratio that fits all--it depends on the species and environment. Actually, what is good mutation today may be bad tomorrow or neutral (or vis-a-versa). Consider sickle cell anemia (http://en.wikipedia.org/wiki/Sickle_cell_anemia), where a single mutation confers advantage for humans (in the heterozygous condition) but only in environment where a species of mosquito is found.

    Here we read a study where 12 % of mutations were beneficial:http://www.pnas.org/cgi/content/abstract/98/20/11388. Here that 35 % (in humans) are beneficial:http://www.uchospitals.edu/news/2002/20020227-evolve.html
    Here that neutral mutations ranged from 18 to 32 %: http://www.bioinf.uni-leipzig.de/Pu...016.pdf#search="percent of neutral mutations". Search the literature, you will find many examples of such percentages.
     
  5. Sep 20, 2006 #4

    jim mcnamara

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  6. Sep 26, 2006 #5

    SF

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    Whether a mutation is harmful, neutral, or beneficial is hard to tell.
    Those that kill you at birth are deffinetly harmful, but what about others?

    You can't say that the only harmful mutations are those that kill you, in fact, you can't even discerne every other mutation unless you put it in "context", aka: in the invironment.

    Phosphorescent fur could save a mouse from a cat, but it would later bring it's doom, at the hand of an over-curious kid.
    You get my point :) It's too random to provide numbers, but generally, I'd say neutral are the most frequent.

    We're all different, but we're not special. (tm)
     
  7. Sep 27, 2006 #6

    Phobos

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    Watch out how you define 'mutation' too. Sometimes people mean any genetic change (including normal recombination during reproduction) and sometimes people mean a copying error or some kind of damage.
    The latter case is more often detrimental than beneficial...not sure about the ratio to neutral changes. Like other said, it depends where it happens (critical gene or not) and what the environmental conditions that the organism has to live in.
     
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