Jacques Monod and the “junk” DNA puzzle

[VladP]

As it seems the ideas of the outstanding microbiologist and evolutionary theorist, 1965 Nobel prize winner, Jacques Monod, 1910-76, may throw some light on the “junk” DNA issue. And they may do upon the paradoxical essence of biological evolution, as well.

He has stated way back, that as regards spontaneous evolution, the crucial part is played by “two things: (i) reproduction true to type of the structure itself, and (ii) reproduction equally true to type, of any accident that occurs in the structure. Once you have that, you have evolution, because you have conservation of accidents”. [Le Hasard et la Necessite, 1970. Cit. by Jacques Monod. Chance and Necessity, 1974., p. 394]

The two conditions appear clear and laconic, and self-replicators which comply with the Monod’s guidelines spontaneously evolve. Indeed, in the case, self-replication is accompanied by cumulative changes. Therefore, the irreversible process of “descent with modification” takes place that is traditionally associated with spontaneous evolution.

 

[Area54]

I think I am missing something here. Perhaps you can help me follow your point.

You suggest Monod's ideas may "throw light" on junk DNA, but you then (apparently) make no mention of what light is thrown and how. Would you explain?

The observations of Monod do not seem qualitatively different from how evolution was perceived a couple of decades, at least, before he wrote them. As I said at the start, what am I missing?

 

 

[VladP]

Dear Area54, so far you are missing nothing at all. The idea in question is quite simple and transparent, yet there is hardly a possibility to consistently expound it in a couple of paragraphs.

And curiously enough, the Monod’s conditions for spontaneous evolution to proceed don’t involve natural selection. This delicate circumstance deserves special attention.

Anyway, I am to continue. For instance, consider prokaryotes that are natural self-replicators. Asexual bacteria satisfy the Monod’s conditions, and so they spontaneously evolve. At that, bacteria fall into the so-called modular self-replicators class. [Eors Szathmary. The Evolution of Replicators. Phil. Trans. R. Soc. Lond. B., 2000] The thing is that in prokaryotic cells, unlike the early syncretic self-replicators, the information modules (genomes) are clearly segregated off those executive, - i.e., off proteins and functional RNAs.

Moreover, a bacterial genome comprises, along with coding fragments, some DNA snippets that are identified as these “junk”. In other words, a genome is segregated into two subdivisions: first, this operational which codes proteins and transcribes functional RNAs. And, second, the enigmatic subdivision which part still remains indistinct.

 

Edited July 26, 2017 by VladP
misprint correction

[Area54]

2 hours ago, VladP said:

Dear Area54, so far you are missing nothing at all. The idea in question is quite simple and transparent, yet there is hardly a possibility to consistently expound it in a couple of paragraphs.

In that case perhaps it is not as simple and transparent as you imagine.

And curiously enough, the Monod’s conditions for spontaneous evolution to proceed don’t involve natural selection. This delicate circumstance deserves special attention.

Implicitly they do. For successful reproduction, of original or accidental structure, to occur natural selection is required. Natural selection determines whether the original, or the accidental structure are more favoured in the lottery of reproduction.

Anyway, I am to continue. For instance, consider prokaryotes that are natural self-replicators. Asexual bacteria satisfy the Monod’s conditions, and so they spontaneously evolve.

And that evolution is governed by natural selection.

 

At that, bacteria fall into the so-called modular self-replicators class. [Eors Szathmary. The Evolution of Replicators. Phil. Trans. R. Soc. Lond. B., 2000] The thing is that in prokaryotic cells, unlike the early syncretic self-replicators, the information modules (genomes) are clearly segregated off those executive, - i.e., off proteins and functional RNAs.

Moreover, a bacterial genome comprises, along with coding fragments, some DNA snippets that are identified as these “junk”. In other words, a genome is segregated into two subdivisions: first, this operational which codes genes and transcribes functional RNAs. And, second, the enigmatic subdivision which part still remains indistinct.

 

 

I am generally quite dense. I still have no idea where you are going with this.

[VladP]

Dear Area54, hold your horses. Everything in its own time. Indeed, the idea in question is simple and transparent, yet it is utterly strange. So we are to advance gradually, step by step. And as for natural selection (NS) we’ll get outside of the issue somewhat later.

Well, there are two subdivisions in a genome: this operational – and (as yet) the indistinct one. Unlike the former, the latter doesn’t affect the phenotype, and this is why latter subdivisions don’t experience the NS pressure. Therefore, nothing restricts the accumulation of heritable information there: the indistinct subdivisions may widely expand – and they do expand.

By Monod, a structure spontaneously evolves due to “… (ii) reproduction … of any accident that occurs in the structure”. At that, a self-replicator reproduces accidents which occur within its genome’s subdivisions – both this operational and this indistinct. Suppose, an instruction accidentally emerges in the latter subdivision: duplicate one or another DNA fragment, within the genome. Such an instruction is far and away less complex than the genetic instructions which control, say, the translation or binary fission processes.

[hypervalent_iodine]

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VladP,

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[Area54]

7 hours ago, VladP said:

Dear Area54, hold your horses. Everything in its own time.

I have removed saddle and bridle, brushed them down, given them some fresh hay and secured them in the stable. When you get around to presenting your thesis with clarity and completeness I shall be pleased to return to the discussion.

[VladP]

Well, I’m compelled to come directly to the point: the evolution of modular self-replicators is capable of self-learning (by doing). So, biological evolution is an active purposeful process. The prose of informatics and cybernetics. For detail see advertising removed. Enjoy.

Edited July 28, 2017 by hypervalent_iodine
advertising removed

[hypervalent_iodine]

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