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Thread: synthesis from DNA

  1. #1 synthesis from DNA 
    Moderator Moderator AlexP's Avatar
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    Could someone place the DNA (all of it) of a very simple organism, such as a bacterium, in a solution containing everything found in the formed organism in a useable form, and expect a living organism to be formed?


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  3. #2  
    Him
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    Forum Sophomore Him's Avatar
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    I think I catch your drift. My answer would be: no I do not expect a living organism to be formed. Bacteria are far too complex and can not be compared with most early self replicating molecules which form the basis of live on earth.


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    Quote Originally Posted by Him
    I think I catch your drift. My answer would be: no I do not expect a living organism to be formed. Bacteria are far too complex and can not be compared with most early self replicating molecules which form the basis of live on earth.
    Exactly, a bacteria is much more than the DNA. Without the others componements the DNA is totally worthless. DNA is just the book of instructions : without the factory, able to achieve the instructions, it's totally worthless.
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    thanks for the replies. so, now i'll ask the same question for the simplest living organism...whatever that is. an Archaea maybe? which i think would be a bacterium. so yeah, take the DNA of the simplest living thing (let's include viruses in that) and put it under the same conditions. any results?
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    Forum Masters Degree invert_nexus's Avatar
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    There's a problem with your premise:

    and expect a living organism to be formed?
    Life is an ambiguous term. Especially when dealing with such simple organisms as this.

    What would happen is that many processes that take part in a living organism would take place.
    You've stated that all the ingredients of a cell are in the mix, so there is no reason why the chemical processes which take place inside the cell wouldn't also take place in the test tube.

    Of course, they'd only go to equilibrium. A vital aspect of cellular function is to manipulate chemical reactants and products so as to cause chemical reactions to start and stop at key moments.


    But, other processes wouldn't take place.

    Bacteria depend upon a proton-motive force which builds up along the cell membrane because of proton pumps and other membrane proteins.
    This proton-motive force powers ATP production.

    The contents of your beaker wouldn't be enclosed within a lipid membrane and thus would be deprived of their primary ATP power source. Without ATP many cellular processes wouldn't be able to operate.

    In eukaryotes, this process takes place inside the mitochondria which has its own membranes. But the chemical process is remarkably similar.

    Just what do you mean when you say 'everything found in the formed organism in a useable form'?

    Are ribosomes present?
    Lipid membranes?
    Every organelle?
    Every protein?
    Every structure?

    There must be some point where we must say that the structure is limited, otherwise you'd have a cell rather than an amalgam of parts. But, where to draw the line?

    Remember that labels are just that. In reality, the distinction between parts is not so easily discerned. The labels are merely a convenient method for modeling the situation.


    As to your second question... I'm unsure exactly about how the Archaea create ATP, but suspect that it utilizes the cell membrane in the same fashion as bacteria. Therefore, if the contents are not encased in a lipid membrane, then you do not have the most vital process constituting 'life'.


    As to viruses, they depend upon the cellular machinery to operate. Therfore, if you place virus parts in a beaker they won't do anything. Perhaps portions of them might self-assemble, but much of the assembly also depends upon cellular machinery so it's doubtful that in most cases a successful virus would be assembled. I suppose that there are probably some few extremely simple viruses that could completely self-assemble; but I have no direct knowledge of this or which might be likely candidates.
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    ok, i realize that i wasn't being very specific. sorry about that.

    there are no ribosomes, no membranes, no anything with structure above the molecular level... i'm thinking along the lines of the urey-miller experiment. there's methane, ammonia, oxygen, phosphorous in some form, sulfur in some form... i think those are the main ingredients that are necessary for a living thing, right? but unlike the urey-miller, there are no sparks, nothing to facilitate the formation of structures except the genetic info encoded in the DNA in the solution. does the DNA have the 'intelligence' to put these things together? or even to just form a ribosome, which i believe would be necessary for protein synthesis?
    "There is a kind of lazy pleasure in useless and out-of-the-way erudition." -Jorge Luis Borges
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    Forum Masters Degree invert_nexus's Avatar
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    Simple answer?

    No.

    There might be some simple reactions to equilibrium.

    There might also be some simple assembling molecules.

    But, the vast majority of components necessary for cellular mechanics would not self-assemble.

    Life came up in stages. It is debatable which elements came first. Metabolism or replication. But, whichever came first, the earliest processes were far different than those that are built up in modern organisms.


    I was just reading a news story from ScienceNOW about sphalerite, a compound found at hydrothermal vents which provides three of the five necessary components to start the Krebs cycle.
    However, even if all the necessary components of the Krebs cycle were present, the cycle wouldn't be carried out as the levels of reactants would not be actively manipulated by other cellular processes.

    http://sciencenow.sciencemag.org/cgi...ll/2006/1208/3

    Of course, YOU could take part and manipulate levels of reactants within the beaker and keep various reactions going, however, you wouldn't be able to do a very good job of it.


    Anyway.
    The prospect is simply out of the question.
    Life, in its current form, is supremely adapted for its environment. And environment which does not exist in the gedanken you've proposed.

    DNA would likely be denatured in this environment.


    or even to just form a ribosome, which i believe would be necessary for protein synthesis?
    Not only the ribosome, but also the tRNA. It is in the tRNA which the code for reading DNA is found. This code also evolved over time. And without this code, the DNA is nothing.

    Also required would be ATP. Which would entail the necessity of ATP synthase.

    Also, the various amino acids would be required.

    The number of cellular mechanisms required would constantly grow by association until you, in the end, would have to have an entire working cell.

    This would not simply self-assemble.
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  9. #8  
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    No. DNA in its self is just a molecule.
    It requires enzymes, such as RNA polymerases, to have its message mean anything.
    It is not so much that I have confidence in scientists being right, but that I have so much in nonscientists being wrong. --- Isaac Asimov
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