Which Came First...

[EWright]

DNA or the cell?

[damocles]

DNA or the cell?

 

I don't know; but if I had to test for this, I'd make that question a testable part of a sequence of abiogenesis experiments to find out.

 

I would initially test to see if DNA organized first enroute to the cell structure appearing or if DNA came after a cell with RNA formed.

 

That might answer your question.

 

What do I guess the result might be?

 

The simpler structure should appear first. But DNA is such a fragile molecule, I don't know if it would need a cell wall to protect it so that it could exist for extended periods of time and replicate itself. That would be another question I would test as part of a cell formation hypothesis.

 

Best wishes;

[GAHD]

I'd bet RNA came first.

[HydrogenBond]

RNA seems to have come first due to it being present in the simplest life forms. The current theory is that simple RNA replicators are the percursors of life. Once that basic dynamics was worked out by nature, nature was able to build from there, including using DNA. DNA testing uses a simple process that makes DNA duplicates.

[EWright]

RNA seems to have come first due to it being present in the simplest life forms. The current theory is that simple RNA replicators are the percursors of life. Once that basic dynamics was worked out by nature, nature was able to build from there, including using DNA. DNA testing uses a simple process that makes DNA duplicates.

 

So did RNA initially have a cellular housing? Or is there evidence that it developed outside of a cellular environment, and would this even be possible?

[HydrogenBond]

I am not mistaken the exisiting belief is that it occurred initally outside the cell membrane. It was just RNA strands acting as templates making more RNA via simple polymerization, then separating apart, since the RNA double helix is not stable. Containment within a membrane, i.e, primal 10-20 carbon polyethelene, shrinks its environment such that making RNA becomes more sporadic and less complete. This creates smaller chunks for other things that is not genetic, such as ribosomal RNA , which are too big to escape the containment. If RNA could form than it would be reasonable that environmental polymerization of amino acids should have also occurred. These simple proteins maybe stuck to the membrane or got inside the little eco-systems. This alterred the internal environment especially for the small RNA, maybe leading to catalysis for animo acid polymerization.

[CraigD]

… is that first came a mish-mash of proteins with varying degrees of replicating ability,

then came RNA,

then DNA,

then DNA surrounded by a protein sheath (viruses),

then, via a fairly smooth evolutionary continuum, viruses with some self-replicating ability,

cells with weak replicating abilities (poor transcription),

and, finally, “modern” cells (good transcription).

 

An implication of my guess is that improvements in cell mechanics is an ongoing evolutionary process, so future cells may be “better” than current ones.

[lindagarrette]

I am not mistaken the exisiting belief is that it occurred initally outside the cell membrane. It was just RNA strands acting as templates making more RNA via simple polymerization, then separating apart, since the RNA double helix is not stable. Containment within a membrane, i.e, primal 10-20 carbon polyethelene, shrinks its environment such that making RNA becomes more sporadic and less complete. This creates smaller chunks for other things that is not genetic, such as ribosomal RNA , which are too big to escape the containment. If RNA could form than it would be reasonable that environmental polymerization of amino acids should have also occurred. These simple proteins maybe stuck to the membrane or got inside the little eco-systems. This alterred the internal environment especially for the small RNA, maybe leading to catalysis for animo acid polymerization.

There mus tbe some natural "law" that makes replication (and evolution) necessary. Yet as far as we know, nature is uncaring, unporposeful, and passive. As an athiest, I certainly don't believe anything supernatural is at work here. Point is, if our planet experienced this natural tenacity for life, it must be a universal. Wherever the conditions are right, it will happen.

[damocles]

… is that first came a mish-mash of proteins with varying degrees of replicating ability,

then came RNA,

then DNA,

then DNA surrounded by a protein sheath (visuses),

then, via a fairly smooth evolutionary continuum, viruses with some self-replicating ability,

cells with weak replicating abilities (poor transcription),

and, finally, “modern” cells (good transcription).

 

An implication of my guess is that improvements in cell mechanics is an ongoing evolutionary process, so future cells may be “better” than current ones.

 

Okay, I'm missing something here obviously. Most modern viruses hijack a cell to replicate themselves, yes?

 

How did these first viruses eat? :confused:

[CraigD]

Okay, I'm missing something here obviously. Most modern viruses hijack a cell to replicate themselves, yes?

Yes. However, modern viruses are modern, which the ones I’m proposing are ancient, and likely all or nearly all extinct. Once cells with nuclei became prevalent, these “viruses with some self-replicating ability” would have been at a disadvantage to modern viruses, and would have quickly become extinct.

How did these first viruses eat?

It’s arguable that modern viruses “eat” – they’re accurately described as single-purpose biochemical machines, where, as you note, that purpose is to hijack a cells DNA replication factors to replicated themselves. The very limited amount of physical work they can do is due to energy-storing protein configurations, just enough to deliver their DNA package to the next cell nucleus or nucleoid.

 

If I’m consistent with my virus evolving into true cell model, though, then modern cellular organelles, such as mitochondria, also have ancient viral ancestors. These ancient viruses would have had biochemical capabilities similar to the organelles they evolved into, so, unlike modern viruses, must have had a kind of primitive metabolism, granting it the ability to reform its proteins thought chemical reactions – in other words, to “eat”. These primitive mechanisms form the basis for the what would evolve into modern cellular energy conversion.

 

Bear in mind I’m guessing. I’m not expert in molecular biology, and there’s not much chance of finding a record of these hypothetical ancient life forms. Also note that I’m proposing an unconventional description of very early evolution, in disagreement with the consensus of properly educated biologists. While I find the idea appealing, and in agreement with my intuition of the nature of biological structure and evolution, it’s quite likely to be just plain wrong. If I am correct, however, the supporting evidence will be either:

1. Finding modern versions of these ancient viruses, hybrids of cell and virus. Having been driven from the prime nitches by modern cells and viruses, this will be a tricky hunt, but at least a scientific one; or
   
2. Developing a simulation of molecular biology powerful enough to allow the simulation of the proposed evolutionary process. IMHO, such simulations offer the best hope of a detailed understanding of early biological evolution.

[CraigD]

There mus tbe some natural "law" that makes replication (and evolution) necessary. Yet as far as we know, nature is uncaring, unporposeful, and passive. As an athiest, I certainly don't believe anything supernatural is at work here. Point is, if our planet experienced this natural tenacity for life, it must be a universal. Wherever the conditions are right, it will happen.

The law who’s existence you’re asserting could be a simple, numeric one. In a “primordial soup” of replicating and non-replicating chemical systems, the most rapidly replicating ones would quickly achieve numeric domination of the ecosphere. I suspect that Novel non or poorly-replicating chemical systems spontaneously emerge into the modern ecosphere fairly frequently, but don’t last long, being either out-competed or out-right eaten by more fit modern organisms, making the prospect of finding and identifying such weird beasties remote.

[Fishteacher73]

The law seems to be IMO simple therodynamics. Even in chemistry you have a vague replication of survival of the fittest. Given a mix of chemicals, depending on the environment and the selection of constituants, you will have a specific product. Change the conditions and you may have different products. You will have this "competition" for resources and only the most energetically favorable result will occur. Change the condidtions (but not the constituants) and you may have a different product. In a soup-type mix as proposed to be the ancient oceans, each result alters the constituants and drives reactions onward. You begin to get more and more complex molecules, each "competing" for various reactants to form more and more energetically favorable molecules. In a way a series of chemical punctuated equilibria.

 

Given the environment and constituants of the primordial earth, perhaps complex organic molecules becomes the logical outcome to a long series of shifting equlibria.

[HydrogenBond]

The soup of life was probably very simple molecules like, water, phophate, ammonia, carbonate, acetate, nitrate, etc., . Within the hot earth and maybe the hot UV sunlight which can break bonds, slightly more complex but stable materials formed like animo acids, something resembling simple lipids, nucleic acids, etc.,, These undergo simple polymerization. The result are simple proteins, RNA/DNA and membrane. The combinations from there appear endless with natural selection making certain combos more self perpetuating.

 

To reach a cell from these building blocks is assumed to be a long random process to which their are many possible and reasonable scenarios. This assumption may not be the case. The one variable that is everywhere within the living state, at all times within its evolution, is hydrogen bonding. All the proteins, DNA, RNA and water are all dependant on hydrogen bonding to define their structures, chemical properties and activities. Without hydrogen bonding any expression of life, cellular or multicelluler, modern of primal would regress back to the sludge of life. The proteins would unfold, the DNA double helix would separate, the water would vaporize. Add the hydrogen bonding back and life reappears from disorder. Maybe the increasing complexity of the hydrogen bonding of life is the natural path of life. Rocks and semi-conductors are dependant on electrons. This is also true for the living state, but the living state also needs the activity of hydrogen protons to organize and animate these chemicals into the dynamics of life.

 

We need to focus more on the hydrogen proton because the evolution of life may be hydrogen proton moving up or down an energy curve. The snowball starts small but gets bigger and fancier as it rolls down the energy hill.

 

To help be less nebulous, the sun, via photosynthesis, makes reduce carbon or hydrogen protons of low energy with extra electron density to stabilize its postive charge. All cells used this these reduced protons to make oxidized protons, such as the hydrogen protons which exist within water. Between these two potentials, the living state spreads out further and further with subtle intemediate step down complexity. Single cells can only take the spread so far, then we need multicellular to go further. Finally nervous tissue and the brain fill in the spread further still.

 

If one looks at the brain it allows this simple potential to be amplied. The diversity spread within the base potential appears to be going in the direction of hydrogen proton amplification, since even muscular work requires hydrogen bonding. Within single cell, the cells that are better adapted to the environment have selective advantage because their hydrogen proton signal becomes amplifed outside themsevles, i.e, ion pumping, into the hydrogen bonding of the water outside the cell, allowing them to also adapt their environment to their own needs. Even a virus will adapt and amplify its eefect on its environment by hydrogen bonding to a host cell.

[EWright]

… is that first came a mish-mash of proteins with varying degrees of replicating ability,

then came RNA,

then DNA,

then DNA surrounded by a protein sheath (viruses),

then, via a fairly smooth evolutionary continuum, viruses with some self-replicating ability,

cells with weak replicating abilities (poor transcription),

and, finally, “modern” cells (good transcription).

 

An implication of my guess is that improvements in cell mechanics is an ongoing evolutionary process, so future cells may be “better” than current ones.

 

So all life evolved from viruses? And so humans are essentially the most advanced virus in the history of the planet. And now we're creating the means, through the overuse of antibiotics, for superviruses to evolve into who knows what!? Thus we are just a catalist for an even more advanced species that will arise billions of years from now. Wow, those viruses are some pretty tricky characters! They'll probably even use our own evolved/advanced framework to build on! And then there are the computer viruses that us advanced viral species are creating.... whoa!