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Science Forum

  1. 05 Mar '08 16:21
    please, don't come up with theological theories.

    All life that ever existed on earth seems to be RNA-DNA based. This definitely evidences an original life from which all life forms evolved.

    But imagining earth back then, I would say many different kinds of complex molecules aggregations could form. Why did only nucleic acid based ones survive?
    If we could redo the experiment do you think nucleic acid based proto-organisms would be the dominant ones?

    I think the ones that survived were the most unstable ones (propense to mutations). But I can imagine life forms whose building blocks wouldn't be C,N,O,H based.
    Or CNOH based, but using very different mechanisms.
  2. Subscriber coquette
    Already mated
    05 Mar '08 16:25
    not only DNA "survived" and thrived, amino acids did too

    but

    DNA has one charming ability . . .it reproduces itself. that's a pretty important part of life
  3. 05 Mar '08 16:33
    Originally posted by coquette
    not only DNA "survived" and thrived, amino acids did too

    but

    DNA has one charming ability . . .it reproduces itself. that's a pretty important part of life
    I would say there should be different kinds of life present, not protein based. (maybe not even CNOH based).
    There are other unstable elements that can group spontaneously and interact. But everything is carbon based and even more difficult: protein based.
    Is there such a greater competitive advantage of protein based life forms in this planet?
  4. 05 Mar '08 16:47
    Originally posted by serigado
    please, don't come up with theological theories.

    All life that ever existed on earth seems to be RNA-DNA based. This definitely evidences an original life from which all life forms evolved.

    But imagining earth back then, I would say many different kinds of complex molecules aggregations could form. Why did only nucleic acid based ones survive?
    If we ...[text shortened]... ilding blocks wouldn't be C,N,O,H based.
    Or CNOH based, but using very different mechanisms.
    Regarding Life forms not made from C,N,O,H:

    In order to be the building block of life (as we know it), an element needs the following (out of the top of my head, you might want many more attributes):

    1. To be common.
    2. To form bonds (Helium is out of the question! :-) ).
    2a. Some of them will need the ability to form complex structures - thus, more then two bonds.
    3. To form bonds that are both stable enough for complex structures to exist and not too hard to break so you could disassemble them.
    4.To be able to form the basis for energetic reduction/oxidation reactions, in order to store and release energy.
    5. To be able to form non-covalent bonds (all bonds referred to above are covalent).
  5. 05 Mar '08 16:59
    Originally posted by serigado
    Is there such a greater competitive advantage of protein based life forms in this planet?
    Consider that abiogenesis is rare - it is very difficult to get life "off the ground" so to speak. It is very probable that no life form that uses something in the place of protein was there to compete with our ancient bacterial ancestors - And, if such a life form, one that uses something else instead of proteins, evolved after protein using life forms were already up and running, the new comers will probably be far behind the already complex and sophisticated "protein users", and will not be able to compete with them.
  6. 05 Mar '08 16:59
    Originally posted by Retrovirus
    Regarding Life forms not made from C,N,O,H:

    In order to be the building block of life (as we know it), an element needs the following (out of the top of my head, you might want many more attributes):

    1. To be common.
    2. To form bonds (Helium is out of the question! :-) ).
    2a. Some of them will need the ability to form complex structures - thus, mo ...[text shortened]... se energy.
    5. To be able to form non-covalent bonds (all bonds referred to above are covalent).
    Agreed.

    Just found this
    http://en.wikipedia.org/wiki/Graham_Cairns-Smith

    exactly what I was expecting. There might be some very simple and basic non-carbon based organisms, that would hardly survive.
    But forgetting about non carbon life.... Why did life evolve exclusively with protein replicated organisms? There should be other mechanisms!
  7. 05 Mar '08 22:14
    Originally posted by coquette
    not only DNA "survived" and thrived, amino acids did too

    but

    DNA has one charming ability . . .it reproduces itself. that's a pretty important part of life
    But, does DNA reproduce itself? It needs enzymes to reproduce.
  8. 05 Mar '08 22:28
    Originally posted by serigado

    I think the ones that survived were the most unstable ones (propense to mutations).
    Mutations aren't necessarily detrimental and damaging, some happened to be advantageous as well.

    Beauty of life is in its flexibility and adaptability to changing environment. Look at stable chemicals such as repetitive inorganic crystals.. what are they capable of?
  9. 05 Mar '08 22:48 / 1 edit
    Originally posted by znsho
    But, does DNA reproduce itself? It needs enzymes to reproduce.
    I quite like the idea of self-replicating DNA. Forensic labs would appreciate that, I suppose

  10. Subscriber coquette
    Already mated
    05 Mar '08 22:57
    Originally posted by znsho
    But, does DNA reproduce itself? It needs enzymes to reproduce.
    enzymes make reactions go faster, they don't make reactions happen
  11. Subscriber coquette
    Already mated
    05 Mar '08 22:59
    water (with heat, acid-base, and solvent properties), carbon chemistry (organic co-valent bonds), amino acids (building blocks for protein), necleic acids (for reproduction) and energy, and you will inevitably end up with a tax collector
  12. 05 Mar '08 23:00
    Originally posted by coquette
    enzymes make reactions go faster, they don't make reactions happen
    But enzymes also guide which directions a particular molecule can follow. DNA alone would be highly unlikely to replicate since it has so many other 'choices' to follow, not least degradation.
  13. 05 Mar '08 23:13 / 1 edit
    Originally posted by coquette
    water (with heat, acid-base, and solvent properties), carbon chemistry (organic co-valent bonds), amino acids (building blocks for protein), necleic acids (for reproduction) and energy, and you will inevitably end up with a tax collector
    Having nucleic acids only does not mean that "it" is capable of reproduction on the earth.
    (e.g. viruses cannot replicate independently without infecting a host cell to utilise its machinery)

    Nucleic acids are just like a set of instructions. DNA is a master copy and RNA is a print-out for a short-term.

    Don't tell me off for stating obvious...........
  14. 06 Mar '08 08:46
    Originally posted by coquette
    water (with heat, acid-base, and solvent properties), carbon chemistry (organic co-valent bonds), amino acids (building blocks for protein), necleic acids (for reproduction) and energy, and you will inevitably end up with a tax collector
    LOL, you can't be serious...
  15. 06 Mar '08 08:50
    Originally posted by znsho
    But, does DNA reproduce itself? It needs enzymes to reproduce.
    That's were the "RNA world" hypothesis fits in.

    RNA can both store information (although DNA is better at it) AND catalyze reactions (although proteins are better at it).

    http://en.wikipedia.org/wiki/RNA_world_hypothesis