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Thread: which came first the dna or the histoine

  1. #1 which came first the dna or the histoine 
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    i was studying genitics again.. and i was wondering if anyone can answer this question

    if dna stucture PO4-Deoxyribisosnucleaic acid-BASE is held together by histine (excuse my spelling) a proitien, and dna is the code for all proitiens, how did the structure come about,

    ie , the triplets, need to be together, in the double helix to form a proitien, how did histine become to hold it together if it cnnot be made?

    same goes for the enzymes involved in dna replication?

    any answer? :?


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    Good question!

    Answer is: nobody has figured this out yet. We will one day, however.

    I believe the first step in life wasn't DNA or RNA at all. It rather was the formation and replication of lipophile vesicles. Vesicles are an earlier requirement. As any chemist knows, it is a requirement that the biochemical molecules need to be concentrated enough to produce the desired product chemical reactions, and that the molecules of biochemistry be isolated from being dispersed into the environment, and the deleterious molecules from the environment need to be prevented from entering into and interfering with the precious biochemical reactions.

    So this means the first step of life was whatever chemistry caused replication of simple lipophile membranes. My guess is that the lipophile molecules were synthesized over a template, because these molecules need to all have about the same structure to make a stable vesicle. The template may have been a clay (there are chemical literature references to clays being good for templated synthesis).

    My next guess is that the vesicles had to concentrate and I suupose eventually synthesize the precursors to new vesicles - thus allowing for replication. This doesn't require DNA. Possibly these precursors were certain amino acids. After these were synthesized, the templating surface could be used to polymerize these into lipophile molecules, and bud new vesicles.

    One could go on for here, speculating about how the templating moved from a surface reaction on a regular solid (clay) to a molecule such as DNA. It's a lot of speculation!

    But I have no doubt that within the next 50 years and probably much less, a plausible artificial self-replicating system using amino acids within a lipophilic vesicle will be demonstrated in someone's chemical labs.


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  4. #3  
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    good answer , although your right, too much speculation

    but i suppose time will tell,
    its sorta hit an miss . the amino acids just happened to form , in the right manner and fold in the right way,

    i suppose its the same as the life question.

    good answer, cheers
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    Actually I think the first step was RNA. RNA can also form secondary, tertiary and quaternary structures and can perform as many functions as proteins, just not as efficiantly.

    An example from our age are self splicing mRna segments, in general sich RNA is called ribozyme.

    I dont believe that lipophile membranes were there from the beginning because they are not needed by self catalysing, self replicating RNA cycles.

    Anyway, what is the structure of such a vesicle? If its like the membranes we have, then nucleotides wouldnt be able to pass through due to their negative P groups.
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    I dont believe that lipophile membranes were there from the beginning because they are not needed by self catalysing, self replicating RNA cycles.
    Lipophile vesicles are needed to segregate all the other biochemical reactions, and to have a high enough concentration of amino acids to replicate RNA.

    There has been some demonstration of replicating vesicles in the lab already.
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    Quote Originally Posted by silylene
    I dont believe that lipophile membranes were there from the beginning because they are not needed by self catalysing, self replicating RNA cycles.
    Lipophile vesicles are needed to segregate all the other biochemical reactions, and to have a high enough concentration of amino acids to replicate RNA.

    There has been some demonstration of replicating vesicles in the lab already.
    Yeah but at the point of which Im talking about, aminoacids arent significant yet because the process of replication is catalysed also by RNA.

    Every role is being played by RNA at this point.
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    Well then, believe what you want, since we don't know and it's all speculation.

    The vesicles came first. Had to. There was no naked RNA running around.
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    Cairns-Smith
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    The Cairns-Smith theory is very interesting, but I really dont see why its more probabile that the RNA world theory.

    What I find is really convincing about the RNA world theory, is that experments have shown that nucleotids and oligonucleotides form under the conditions of the primordial atmosphere.
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  11. #10  
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    I think the conclusive answer can’t be found; but also this conclusion has been put forward.
    However the replication of vesicles look like a quite complex mechanism to me. And surely they are not necessary for the self-replicating functions RNA can have (like silyene also mentioned). Such vesicle indeed concentrate and shall improve progress of RNA catalysis, but they are not essential.
    And again to obtain any form of organised reactions such vesicle are necessary.

    It will stay a guess for me.
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