How did our genetic process get set up?

[Isaac0427]

In bio we are learning about genetics; DNA replication, transcription and translation. The process from DNA to proteins is extremely, extremely complex (not understanding it, just the mechanics of it). It just seems like a weird thing to come up naturally. Now, I am not a believer in inteligant design, so I don't want to sound like I am, but I have to ask; the process seems too "well-thought-out" to be natural. I know that it is natural, but is there any scientific explanation as to how that process came about, or how it would come about naturally in an organism. It seems like there has to be something biochemical behind it; it happens in almost every organism.

Thanks!

 

[Andrew Mason]

It's just natural selection over long periods of time. In the primordial sea before life began the were no biological processes working to break down molecules. So they just kept getting randomly more complicated. That is until a lipid sac of molecules emerged that had the ability to use the molecules around it to build more copies of itself. With the ability to reproduce,.these moleecular sacs quickly predominated and life started evolving.

That is relatively easy to explain. The hard part is figuring out how the universe and the laws of physics came into being.

AM

 

[Ygggdrasil]

The question of the origin of life and abiogenesis—how living systems arose from non-living components—is still an active area of research that we don't fully understand. Current thinking is that life began with a "RNA world" in which RNA acted as both the genetic material and as the primary catalyst. Peptides may have been next to evolve, which would form complexes with the RNA to produce ribonucleoprotein complexes that would eventually evolve into proteins. DNA would have evolved later as a more chemically stable storage media than RNA.

For more information see https://www.ncbi.nlm.nih.gov/books/NBK26876/

 

[Fervent Freyja]

I know that it is natural, but is there any scientific explanation as to how that process came about, or how it would come about naturally in an organism. It seems like there has to be something biochemical behind it; it happens in almost every organism.

The process of science is messy, but the end goal for many scientists is to one day have a better, more unified description for all phenomenon. What you are learning about in genetics might seem unnatural, but it's the result of a lot of proven work. It doesn't offer a seamless concept, but it is much more reliable than theories such as the origin of life. Also, different areas of science are more advanced than others. Some areas need some major cleaning and are way behind with the times, such as evolution- I would like to see this replaced with a more exacting description, down to the genetics. This is slow going, but I think it will happen in the future. Genetics may seem weird, but that knowledge has been applied to save the lives of an untold number of people! It is valid, but just because something works doesn't mean we know how it works, especially not always the physics of it. Think, radium therapeutics a century ago, we didn't have a full understanding of the consequences.

You are right in sensing that there is something biochemical behind it, there are many already working on this. This is very difficult to explain and is more than just coming up with the word molecular sacs. There are numerous so-called theories for the origin of life, but none of these offer any quantitative models. I'm honestly not happy with them. In order to fully explain this process, there needs to be collaboration from almost every field, not just in genetics. For example, just one aspect of it, we need to derive more about the formation and history of the early Earth in order to find this biochemical description- a better understanding of physics than we currently have is also required. One of the largest problems in science, although it has been fruitful, is the compartmentalization of knowledge between fields. This created a discrepancy in communication between different areas in science, like I said, some areas are more behind than others. Like the astrophysics boom a few decades ago, more science was done there than in Earth science. Mysteries remain abound. Now, it isn't as much a problem as before, with better communication between areas of science. We will see great things happen in science within the next few decades!

So no, there is yet a real satisfying explanation for the formation of life on earth. I want to see the physics behind it, something that is supported by what we currently know and is not guesswork.

 

[BillTre]

To add a bit more detail to the initial post (which I would call a thermodynamic answer):

You are basically asking about how the genetic system and our biology originated.
This is currently not fully resolved. However, there are several hints and hypotheses about the issue.

These approaches amount to:
1) figuring out a simpler system from which the current system could be derived, and
2) figuring out how those simpler systems could have evolved in the first place.

An important associated question concerns compartmentalization: At what point did a lipid membrane isolate small parts of the overall local chemical mix?
This would be the beginning of cells, leading to:
1) the beginning of competition among assemblies greater than molecules, and
2) the beginning of the ability of the genetics system to control its local molecular environment, which becomes its cellular environment when its contained in a membrane,
3) the ability to achieve much higher concentrations of reactants than would be found in an open external environment, thus getting chemistry to better go the way you want (and to keep more of the product).

One might say it quantized life, as opposed to not having membranes and having a big pool of biochemistry going on with a bunch of different genetic information mixed together in rather random proportions.
One might also say: the effective limits of molecular control are pretty small, so small units might as well be walled off for better control. Longer range communications would have to be between the cellular units.

The dominant hypothesis for the earlier stages of this is now probably the RNA world idea where there is not DNA or proteins yet, just RNA.
Besides being a polymer molecule which can (like DNA) encode information in its sequence (sequence of different monomers), be sitting around, it also is storing information (the current function of DNA), RNA can take sequence specific physical conformations (current examples: tRNA, ribosomal RNA), which can at times have enzyme-like activity (a major current function of proteins), do self-replication (to some extent). A critical thing to achieve, on the way to life, is generating self-replicating information-containing molecules. They would also have to replicate the “genes” for the other ribozymes providing other molecular services of various kinds in order for the local metabolism to function enough for a self-replicating RNA to function. This would be its permissive local molecular (or cellular) environment. Without that its adaptations would be useless.

Next step might be the assembly of peptides and proteins based in some way on the RNA sequence. Eventually the process would be assisted by (if not originally established with) tRNA–like structures (able to pair bond with the RNA sequence) to match amino acids to the RNA in a sequence specific manner. In either case, the amino acids strung along the RNA sequence would polymerize in some way to make peptides and proteins.

A mature biological system would also need a ribosome to more efficiently assemble proteins from the tRNA-amino acids. Much of the ribosome is RNA which have some enzymatic properties.
At this point, there might be a DNA-like storage RNA, mRNA like sequence conveying information for protein synthesis, RNA enzymes, tRNAs, and a ribosome-like protein assembly.

RNA can store information, but DNA is a more stable and better storage medium. Eventually DNA becomes the long-term information storage medium and mRNA’s become an intermediate message used in the construction of certain protein sequences.

At some point, membranes enclosed a cellular space containing the replicating molecules and their required support systems.
This is important because:
- the cell can then develop mechanisms to control its internal environment.
- Ion levels are controlled (or death will happen in most environments)
- Special contents (energy rich molecules or informationally unique molecules it took a while to evolve) will not just float away. Cell interiors are dense with these special items which can give them a competitive advantage over other units. This allows more efficient competition and therefore probably faster evolution.

The genetics/transcription/translation system can not just start itself from nothing. It needs a cellular (or local small scale) environment in which the components of the system (or a slightly more primitive but still compatible set on components) provide a permissive environment for the genetic information to be adaptively expressed. Since the components of the cellular environment can eventually be replaced by new productions from the genetic system, the genetic system also controls the cellular environment (but with a time lag). It can not however boot start it up from nothing. This is a big issue in the beginning of living systems (on earth). It had to be a gradually assembled system in some way.

 

[Andrew Mason]

To add a bit more detail to the initial post (which I would call a thermodynamic answer):

You are basically asking about how the genetic system and our biology originated.

I may misunderstand your point, but I don't think the OP was using a thermodynamic (ie. second law) argument.

It seems to me the he was just saying that the complexity of the simplest life form at the molecular level makes it hard to believe that it started naturally. He was asking how it could have occurred without some unnatural process taking place to get it going.

So the answer to that general question, it seems to me, should be a general one as well: that complexity can evolve naturally with enough of the right kind of atoms interacting through enough processes driven by enough energy taking place over a long enough time period and natural selection.

Just because we don't know the details about how life started does not mean we cannot say that it could have started naturally. It could have started by some alien being flushing out the waste system in its spaceship as it zipped past our solar system, but the only evidence we have is that it originated spontaneously here on Earth naturally.

AM

 

[BillTre]

Opps. Sorry.
I ment your post (2nd not 1st post) was a thermodynamic argument:
Enough time with on going process searching through a complex of different possible solutions.

My answer was more mechanistic details.

 

[BillTre]

Just because we don't know the details about how life started does not mean we cannot say that it could have started naturally. It could have started by some alien being flushing out the waste system in its spaceship as it zipped past our solar system, but the only evidence we have is that it originated spontaneously here on Earth naturally.

This possible, but would only put of the put of the explanation of the origin to another planet.

 

[Evo]

This possible, but would only put of the put of the explanation of the origin to another planet.

But then it just begs the question, how did life start on that planet? We don't know, this is too speculative. Thread closed.