Prebiotic Chemistry to Present Day DNA

[jerrywickey]

Mile stones between prebiotic chemistry to present day DNA based life

 

 

Organic Chemistry

 

(no evolutionary principles apply yet)

 

First replicator

 

(fundamental principles of evolution apply for the first time)

 

Something analogous to if not Ribozymes (serving only as enzymes) or Nucleic Proteins But limited to only what can arise spontaneously again and again for each generation of replicators.

 

(This is the toughest time for replicators, since natural selection still can not operate on the enzymes and nucleic proteins that may have arisen.)

 

Replication of Information Describing Organisms (possibly nucleotides) Coincident with Active Metabolism (This is the single most important step required for further growth toward current biology)

 

AND

 

True Riboszymes (serving a ribosomal function to interpret the information) and Nucleic Proteins carried over from the previous generation.

 

would have had to arise independently and coincidentally

 

(only after both previous steps, can natural selection begin to select superior advantages to replication) (replication becomes reproduction)

 

A switch to DNA with nucleotides if not already nucleotides

 

DNA Polymerase

 

DNA Transcriptase

 

Ribosome

 

True Protein

 

(evolution proper would begin to apply here)

 

Current Observed Biology

 

 

What's wrong here, anything? Are there any steps that could be skipped?

 

Can anyone suggest a different order?

 

Are any steps missing? Do we need all these steps?

 

Jerry

[lucaspa]

What's wrong here, anything? Are there any steps that could be skipped?

 

Can anyone suggest a different order?

 

Are any steps missing? Do we need all these steps?

 

Jerry

 

You are working on the RNA World hypthesis of abiogenesis. There are alternatives. there are some problems with your system and I'll give you an alternative later.

 

First replicator

 

(fundamental principles of evolution apply for the first time)

 

Something analogous to if not Ribozymes (serving only as enzymes) or Nucleic Proteins But limited to only what can arise spontaneously again and again for each generation of replicators.

 

(This is the toughest time for replicators, since natural selection still can not operate on the enzymes and nucleic proteins that may have arisen.)

 

As you noted, natural selection can work on the first replicators. For the ribozymes to continue to exist, they must be composed of replicators or replicators must give rise to them. Thus, natural selection is working. The problem is your premise that ribozymes can not be replicators. In order for RNA to replicate, it must be a ribozyme. IOW, it must catalyze it's own replication.

 

True Riboszymes (serving a ribosomal function to interpret the information) and Nucleic Proteins carried over from the previous generation.

 

Ribozymes are separate from ribosomes. A ribozyme is any RNA that acts also as an enzyme. The smallest is 3 nucleotides long and cleaves U-U bonds. A ribozyme is a system of RNA molecules -- some structural and some ribozymes -- that make proteins from amino acids. And yes, you can have functional ribosomes composed only of RNA. Ribosomes do not have to arise independently of RNA replication. The replicators could easily have 2 capabilities: replicate themselves and be able to function in a ribosome.

 

Also, you don't need to switch to DNA to get directed protein synthesis. RNA can act in the place of DNA. And you would already have to have RNA transcriptase in order to have RNA replication.

 

So, let's give you an alternative route to modern cells:

 

1. Formation of amino acids from primordial precursors (water, ammonia, carbon dioxide, methane, oxygen, hydrogen, etc.) [M-U experiments and Miller and Orgel].

2. Formation of proteinoids by polymerization of sets of amino acids. [Fox and others].

3. Formation of microspheres by contact of proteinoids with water [Fox and others].

4. Synthesis of RNA within the microspheres [Fox]

5. Replication of RNA. [Orgel]

6. Development of the genetic code.

The first 5 steps have been done in the lab. I will be happy to provide a full set of references if you are interested. Fox and others have already shown that some proteins have particular affinity to particular nucleotide sequences. This would be the start of the genetic code.

 

Notice that natural selection begins at step 3.