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Random mutation problem?

  1. Mar 7, 2016 #1
    1.Above sentence means in 1074 mutations(Events) just one of them could make a functional protein and that mutation is beneficial?

    2.Is above sentence similar to "Hoyle's calculation of the Odds of Life", thus the criticism against Hoyle's idea can apply to above sentence?
    Like this:

     
    Last edited: Mar 7, 2016
  2. jcsd
  3. Mar 7, 2016 #2

    Simon Bridge

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    1. I'm reading it as a statement of probability. A 1/e74 probability that a random variation in whateveritwas produces a "functional protein fold".
    That means that if you have a large number of whateveritwas's M, and you count the number of functionally folded proteins N, then N/M will approach 1/e74 as M gets very large.

    If the probability of a success is p=1/n then it is tempting to think we need n trials to get one success ... but that is not the case. You can get a success in just one trial. To see what's going on you can work out the probability of at least one success if there are n trials ... or work out the number of trials m you need so the probability of at least one success is some value you feel good about (0.5, 0.99...).

    2. Need more data... when you quote something, please provide a citation.
    Whether the criticisms apply depends on how the probability was arrived at.

    We can guess: it is claimed to be from empirical data ... so if the probability is measured, then it does not suffer from the flaws in Hoyles argument. But some uses of the figure may do.
     
  4. Mar 7, 2016 #3

    Drakkith

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    Do you have a reference for the first quote?
     
  5. Mar 7, 2016 #4

    Ygggdrasil

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    No. If you write a random sequence of amino acids, very few will fold into stable structures. However, extant protein sequences are not random strings of amino acids, they were selected by evolution to lie in an area of sequence space that form stable folds. Therefore, many mutations to extant proteins have no effect (I think the number is ~50%, but I'll have to check my references later)
     
  6. Mar 7, 2016 #5
    http://www.evolutionnews.org/2014/10/a_reader_asks_c090811.html


    I know it, But i said we need a genetic code for making a functional protein.
    The probability of generate this code by random mutation is 1 in 1074?

    1.All of proteins in organisms that selected by evolution are a functional protein.
    2.Probability of find a functional protein is 1 in 1074.
    3.DNA codes proteins and make them.
    Then probability a random mutation for codes a functional protein is 1 in 1074.
     
    Last edited: Mar 7, 2016
  7. Mar 7, 2016 #6

    Drakkith

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    Your references are from an intelligent design website, and Douglas Axe himself, the author of the paper claiming the 1 in 1074 chance, is a proponent of intelligent design. While that doesn't automatically make his assertions incorrect, it does cast serious doubt on their validity.

    This puts this thread on thin ice. I'm willing to leave it open provided the discussion remains on valid science, but any deviation from that will result in this thread being locked.
     
  8. Mar 7, 2016 #7

    Ygggdrasil

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    A random mutation is different from a random sequence. As an analogy, consider that about 70% of the Earth's surface is covered in water. If you drop a person on a random spot on the globe, the chance they are landing in water is 70%. However, this does not mean that every time you take a step, you have a 70% chance of landing in water. Areas covered by water cluster together on the surface of the Earth as do areas covered by land. If you are on an area covered by land, you have a high probability of finding another area covered by land for each step you take.

    Similarly, if you are starting off at a functional protein fold, then mutating that protein (i.e. changing the identity of one amino acid) is likely to keep you in the area of functional protein folds (according to experimental data, ~62% of amino acid mutations have no effect on function, ~30% are deleterious to function, and 8% appear to be beneficial to function. See http://www.nature.com/nrg/journal/v11/n8/full/nrg2808.html). So once functional protein folds have been found, evolution has ways of diversifying these folds to find other functional protein structures.

    Of course, this begs the question of how the first set of functional protein folds came about in the first place. This is related to work on abiogenesis (the origin of life) and the question is not well understood. It's possible that life began with RNA as the functional molecule, and the first protein-like structures were small peptides that acted as scaffolds to bind and help the RNA molecules to retain their structure. Over time, these small peptides could come to take up more of the structure until eventually you could replace the RNA entirely with protein. It's also worth noting that there are some intrinsically unstructured proteins that still have important biological functions despite not folding into any defined structure. Furthermore, various "low complexity" sequences also have functional roles that rely less on having the protein fold into a specific 3D shape, and could provide a potential route for functional peptides to begin to coalesce into protein-like structures.
     
    Last edited by a moderator: May 7, 2017
  9. Mar 22, 2016 #8
    I'm aware there is some current work going on that suggests that mutations might not be quite as random as was thought, one such idea is a model called Nutrient-dependent/pheromone-controlled adaptive evolution: and there is a lot of interest in the role of viruses in inducing specific changes. As yet I haven't got my head around either but there is quite a lot of literature around about both.
     
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