Replication theory

More information on the square root law and on kinetic and thermodynamic aspects of the minimal replicator theory can be found in the literature (von Kiedrowski, 1999 and 1993). The square root law has its origin in the product inhibition involved in the mechanism of self-replication. The more C units are formed, the greater is the tendency of the molecules of C to dimerize to give C2 this species, however, cannot function as a catalyst. 

Minimal replicator theory I parabolic versus exponential growth. In Bioorganic Chemistry, ed. D. H. Berlin. Springer Verlag, vol. 3, pp. 115 6. 

That view of the origin of life has commonly been called metabolism first the absence of a genetic polymer has been equated with the lack of any mechanism for heredity. As we have seen, replicator theories center on the spontaneous formation of large, information-bearing organic polymers endowed with the ability to copy themselves. The hereditary information carried in the sequence of such a polymer is called a genome. 

ITowever, most normal somatic cells lack telomerase. Consequently, upon every cycle of cell division when the cell replicates its DNA, about 50-nucleotide portions are lost from the end of each telomere. Thus, over time, the telomeres of somatic cells in animals become shorter and shorter, eventually leading to chromosome instability and cell death. This phenomenon has led some scientists to espouse a telomere theory of aging that implicates telomere shortening as the principal factor in cell, tissue, and even organism aging. Interestingly, cancer cells appear immortal because they continue to reproduce indefinitely. A survey of 20 different tumor types by Geron Corporation of Menlo Park, California, revealed that all contained telomerase activity. 

J. vonNeumann, in Theory of Self-Replicating Automata, A. Burks, ed. University of Illinois... 

Independent reference methods - one organization Two or more independent reference methods, each based on an entirely conceptually different principle of measurement, independent in theory and experimental procedure, applied in replicate, within a single organization, of the highest reputational quality, by two or more expert analysts, working independently. The methods used can, naturally, include definitive methods, and the results should be corroborated by a third or additional, independently different, accurately characterized, well established, thoroughly validated, definitive, reference, or other methods. 

DNA has two broad functions replication and expression. First, DNA must be able to replicate itself so that the information coded into its primary structure is transmitted faithfully to progeny cells. Second, this information must be expressed in some useful way. The method for this expression is through RNA intermediaries, which in turn act as templates for the synthesis of every protein in the body. The relationships of DNA to RNA and to protein are often expressed in a graphic syllogism called the central dogma. The concept was proposed by Crick in 1958 and was revised in 1970 to accommodate the discovery of the RNA-dependent DNA polymerase. Crick s original theory suggested that the flow of information was always from RNA to protein and could not be reversed, yet it allowed for the possibility of DNA synthesis from RNA. 

Reproduction is about the propagation of mechanisms of development. Because replication is a special case of inheritance and inheritance is a special case of reproduction, and because reproduction is the progeneration of mechanisms of development, it follows that if transmission genetics is a theory of replication, then transmission genetics is about development as well as about transmission. ... 

In the version of evolutionary theory popularised by Dawkins (1976), the fundamental unit of life is a gene, a conceptual abstraction clothed in the biochemistry of the nucleic acid DNA. The purpose, or telos, of this gene is replication - to make copies of itself - copies which because of random chemical and physical processes maybe more or less accurate. The particular chemical structure of DNA provides a mechanism whereby such faithful copying can readily occur - as James Watson and Francis Crick pointed out... 

The wide gap between the two opposing theories, replication first and metabolism first , was analysed by Pross from the Ben Gurion University of the Negev (Israel). Pross concludes that replication came first He is convinced that a causality between the two theories can only be established if it is assumed that the replication-first thesis is correct. His analysis also shows that more of the experimental results and theoretical rationales favour the replication thesis. The author finds his assumption justified that life processes are strongly kinetically controlled and that the development of metabolic pathways can only be understood if life is considered as a manifestation of replicative chemistry (Pross, 2004). 

The RNA world requires a system capable of self-replication as a precondition for the beginnings of life. In contrast, the surface metabolism theory proposed by Wachtershauser postulates that the initial step is metabolism, from which complex replication systems can evolve later. This metabolism would have occurred at the... 

The results obtained appeared quite promising, but the real sensation was the detection of pyruvate, the salt of 2-oxopropanoic acid (pyruvic acid), which is one of the most important substances in contemporary metabolism. Pyruvic acid was first obtained in 1835 by Berzelius from dry distillation of tartaric acid. The labile pyruvate was detected in a reaction mixture containing pure FeS, 1-nonanethiol and formic acid, using simulated hydrothermal conditions (523 K, 200 MPa). The pyruvate yield, 0.7%, was certainly not overwhelming, but still remarkable under the extreme conditions used, and its formation supports Wachtershauser s theory. Cody concludes from these results that life first evolved in a metabolic system prior to the development of replication processes. 

Eigen s theory concerns itself with phase two, the focal point of the genesis of the replication process. Apart from the first, each phase requires the previous one as its precondition. 

A hypercycle is a more complex organisation form. Its precondition is the presence of several RNA quasi-species which are able to amalgamate chemically with certain proteins (enzymes or their precursors). If such a protein is linked to a quasi-species, the resulting duo favours the replication of a second quasispecies. According to Dyson, the linked populations get stuck in a stable equilibrium. Problems occur at this level Any theory on the origin of replication has the central problem that the replication process must occur perfectly in order to ensure survival . If there are replication errors, these will increase from generation to generation, until the system collapses the error catastrophe has then occurred ... 

How can negative fluctuations in entropy production occur or be triggered As Manfred Eigen shows in his evolution theory, fluctuations in entropy production can be caused by the coming into being of a self-replicating molecular species which is capable of selection. Autocatalytically active mutants can also have the same effect. Looked at this way, the phenomenon of evolution consists of a continuous series of instabilities, i.e., collapses of stationary states. 

It has recently been shown (7) that a transformation from fibrillar to lamellar morphology is not required to replicate the force-temperature profile of stretched networks in the crystallization region. This latest work shows that a close duplication of the behavior of gutta percha (8) can be predicted with a model (7) of fibrillar crystallization that Incorporates several new features omitted in earlier theories, specifically ... 

The theory that life began in an RNA World suggests that the first self-replicating system was a set of RNA molecules. The catalytic and informationtransferring properties of RNA indicate a possible scenario ... 

These ten results represent a sample from a much larger population of data as, in theory, the analyst could have made measurements on many more samples taken from the tub of low-fat spread. Owing to the presence of random errors (see Section 6.3.3), there will always be differences between the results from replicate measurements. To get a clearer picture of how the results from replicate measurements are distributed, it is useful to plot the data. Figure 6.1 shows a frequency plot or histogram of the data. The horizontal axis is divided into bins , each representing a range of results, while the vertical axis shows the frequency with which results occur in each of the ranges (bins). 

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