Neutral theory

Some of the mathematical basis for the equations is due to the geneticist Moto Kimura, who is considered a resolute proponent of the neutral theory of evolution , which states that statistical, chance fluctuations are more important in the formation of new species than is Darwinian natural selection. Evolution via such chance fluctuations is referred to as genetic drift . Dyson considers that both forms of evolution are important (Dyson, 1999). 

Kimura, M., "Recent Development of the Neutral Theory Viewed from the Wright-ian Tradition of Theoretical Population Genetics," Proc. Natl. Acad. Sci. USA, 88, 5969-5973 (1991). 

Kimura, M, (1983) The Neutral Theory of Molecular Evolution (Cambridge Univ. Press, Cambridge, U.K.). 

Molecular phylogeny is a discipline that studies species differences between DNA or protein sequences. Its basic tenet is that during evolution, the sequences have drifted apart by mutation and selection as well as by random drift and fixation of variants in certain positions. The earlier two species separated the more differences became fixed. Phylogenetic trees are constructed on the basis of mutual differences of protein and/or DNA sequence. Comparison of intraspecies variation with between-species variation may in the future yield information on the neutralist/selectionist alternative. McDonald and Kreitman (1991) devised an interesting test against neutrality that compared the ratio of silent/replacement mutation of a given locus within a species with the same ratio between two related species. Under the neutral theory this should be equal (corrected for sample size), but in fact it is not (see Li, 1997, and Hudson, 1993, for a discussion). 

The nucleotide diversity in silent positions may be calculated for a given sample size and sequence length and is about 8 to 10 per 10,000 sites. Estimates of 6 and n (diversity and heterozygosity) were close to each other, as suggested by the neutral theory assuming constant population size (10,000 individuals) under the infinite sites model of population genetics (Li, 1997). 

Gillespie, J. H. (1994). Alternatives to the neutral theory. In Non-Neutral Evolution Theories and Molecular Data. (B. Golding, ed.) pp. 1-17. Chapman Hall, New York. 

The charge neutralizing theory of calcification suggests a fundamental role of organic anions, e. g. sulfated mucopolysaccharides, in regulating bone formation and in retardation of atherosclerosis328). 

Urry, D. W. Neutral sites for calcium ion binding to elastin and collagen A charge neutralization theory for calcification and its relationship to arteriosclerosis. Proc. Nat Acad. Sci. (Wash.) 68, 810 (1971)... 

Kimura, M. (1983). The Neutral Theory of Evolution. Cambridge University Press, Cambridge, U.K. King, J.L. Jukes, T.H. (1969). Non-Darwinian evolution Random fixation of selectively neutral variants. Science 164, 788-798. 

Hubbell SP. 2001. The unified neutral theory of biodiversity and biogeography. Princeton (NJ) Princeton University Press, 448 p. 

A neutral network can arise out of conditions other than strict neutrality. The nearly neutral theory shows that if mutations only slightly disrupt the fitness, then some deviation in the sequence is allowed (Ohta, 1973 Ohta, 1997). This is closely related to the selection strength imposed on the population. In cases where there is a low selection strength, more deviations are allowed and the neutral network is larger. In addition, a neutral network can form due to noise in measuring the fitness (Levitan and Kauffman, 1995). Noise inherently limits the resolution at which selection can detect improvements so small changes are effectively, if not exactly neutral (Newman and Engelhardt, 1998). 

The benefit of neutrality has yet to be captured with in vitro protein evolution. Neutral theory predicts the punctuated emergence of novel structure and function, however, with current methods, the required time scale is not feasible. Utilizing neutral evolution to accelerate the discovery of new functional and structural solutions requires a theory that predicts the behavior of mutational pathways between networks. Because the transition from neutral to adaptive evolution requires a multi-mutational switch, increasing the mutation rate decreases the time required for a punctuated change to occur. By limiting the search to... 

Kimura, M. (1982). Molecular Evolution, Protein Polymorphism, and the Neutral Theory Springer-Verlag, Berlin and Japan Scientific Societies Press, Tokyo. 

In addition to mutation rate, even the other molecular parameters turned out to be different from the expectations of selectionism. It was discovered, for example, that neutral mutations are not in the least a tiny minority with respect to adaptive mutations, and the actual ratio is probably the other way round. At the molecular level, in other words, the dominant mechanism of evolution is not natural selection but genetic drift, and this led Motoo Kimura to formulate the neutral theory of molecular evolution (1968, 1983). 

M. Kimura, The neutral theory of molecular evolution, Cambridge University Press, Cambridge (UK), 1983. 

Karnovsky MJ (1994) Cytochemistry and reactive oxygen species a retrospective. Histochem Cell Biol 102 15-27 Kashefi K, Lovley DR (2003) Extending the upper temperature hmit for hfe. Science 301 934-936 Kasting JF (1993) Earth s early atmosphere. Science 259 920-926 Kenna BT, Kuroda PK (1962) The search for technetium in nature. J Chem Educ 39 436 42 Kimura M (1979) The neutral theory of molecular evolution. 

The results of classical neutral theory are valid only for systems of relatively low population numbers and large genomes. If the genome is large enough that even the 3v one-error mutants cannot be populated because the population number n is smaller than 3v, one may expect the results of so-called neutral theory to be representative. Otherwise, modifications due to the reproducible population of (nearly) neutral mutants, as indicated by the deterministic quasi-species model, pertain and finally destroy the basic assumption of the blind production of mutants at the periphery of the mutant spectrum. 

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