Neutral theory of molecular evolution

neutralneutral evolutionneutral theoryevolutionarily neutralneutral theory of evolutionneutrallyneutral evolutionary processesneutral mutationneutral mutationsbiologically important structure
The neutral theory of molecular evolution holds that most evolutionary changes at the molecular level, and most of the variation within and between species are due to random genetic drift of mutant alleles that are selectively neutral.wikipedia
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Genetic drift

driftrandom genetic driftrandom drift
The neutral theory of molecular evolution holds that most evolutionary changes at the molecular level, and most of the variation within and between species are due to random genetic drift of mutant alleles that are selectively neutral.
In 1968, population geneticist Motoo Kimura rekindled the debate with his neutral theory of molecular evolution, which claims that most instances where a genetic change spreads across a population (although not necessarily changes in phenotypes) are caused by genetic drift acting on neutral mutations.

Motoo Kimura

KimuraKimura, Motoo
The theory was introduced by the Japanese biologist Motoo Kimura in 1968, and independently by two American biologists Jack Lester King and Thomas Hughes Jukes in 1969, and described in detail by Kimura in his 1983 monograph The Neutral Theory of Molecular Evolution.
Motoo Kimura (November 13, 1924 – November 13, 1994) was a Japanese biologist best known for introducing the neutral theory of molecular evolution in 1968.

Jack Lester King

Jack L. KingKing
The theory was introduced by the Japanese biologist Motoo Kimura in 1968, and independently by two American biologists Jack Lester King and Thomas Hughes Jukes in 1969, and described in detail by Kimura in his 1983 monograph The Neutral Theory of Molecular Evolution.
Jack Lester King (March 9, 1934 – June 29, 1983) was an American evolutionary biologist best known for co-authoring (with Thomas H. Jukes) a seminal paper on the neutral theory of molecular evolution, "Non-Darwinian Evolution".

Neutral mutation

neutralconservativenear-neutral
A neutral mutation is one that does not affect an organism's ability to survive and reproduce.
The identification and study of neutral mutations has led to the development of the neutral theory of molecular evolution.

Thomas H. Jukes

Thomas Hughes JukesThomas JukesJukes
The theory was introduced by the Japanese biologist Motoo Kimura in 1968, and independently by two American biologists Jack Lester King and Thomas Hughes Jukes in 1969, and described in detail by Kimura in his 1983 monograph The Neutral Theory of Molecular Evolution.
He was the co-author, with Jack Lester King, of the 1969 Science article "Non-Darwinian Evolution" which, along with Motoo Kimura's earlier publication, was the origin of the neutral theory of molecular evolution.

The Neutral Theory of Molecular Evolution

The theory was introduced by the Japanese biologist Motoo Kimura in 1968, and independently by two American biologists Jack Lester King and Thomas Hughes Jukes in 1969, and described in detail by Kimura in his 1983 monograph The Neutral Theory of Molecular Evolution.
While the neutral theory of molecular evolution existed since his article in 1968, Kimura felt the need to write a monograph with up-to-date information and evidences showing the importance of his theory in evolution.

Polymorphism (biology)

polymorphismpolymorphicmorph
The proposal of the neutral theory was followed by an extensive "neutralist-selectionist" controversy over the interpretation of patterns of molecular divergence and polymorphism, peaking in the 1970s and 1980s.
The work started at a time when natural selection was largely discounted as the leading mechanism for evolution, continued through the middle period when Sewall Wright's ideas on drift were prominent, to the last quarter of the 20th century when ideas such as Kimura's neutral theory of molecular evolution was given much attention.

Population genetics

population geneticistevolutionary geneticspopulation genetic
Many molecular biologists and population geneticists also contributed to the development of the neutral theory.
The availability of molecular data on all genetic differences led to the neutral theory of molecular evolution.

Natural selection

selectionselectiveselected
The theory applies only for evolution at the molecular level, and is compatible with phenotypic evolution being shaped by natural selection as postulated by Charles Darwin.
Motoo Kimura's neutral theory of molecular evolution by genetic drift proposes that this variation accounts for a large fraction of observed genetic diversity.

Evolution

evolvedtheory of evolutionevolutionary
Haldane estimated that it takes about 300 generations for a beneficial mutation to become fixed in a mammalian lineage, meaning that the number of substitutions (1.5 per year) in the evolution between humans and chimpanzees was too high to be explained by beneficial mutations.
The neutral theory of molecular evolution proposed that most evolutionary changes are the result of the fixation of neutral mutations by genetic drift.

Tomoko Ohta

Ohta
Kimura and Ohta also estimated that the alpha and beta chains on the surface of a hemoglobin protein evolve at a rate almost ten times faster than the inside pockets. Tomoko Ohta also emphasized the importance of nearly neutral mutations, in particularly slightly deleterious mutations.
After working on the neutral theory of evolution with her mentor Kimura, she became convinced that nearly neutral mutations (neither deleterious nor entirely neutral) played an important role in evolution.

Nearly neutral theory of molecular evolution

lower selection constraintsnearly neutralnearly neutral theory
Tomoko Ohta also emphasized the importance of nearly neutral mutations, in particularly slightly deleterious mutations.
The nearly neutral theory of molecular evolution is a modification of the neutral theory of molecular evolution that accounts for the fact that not all mutations are either so deleterious such that they can be ignored, or else neutral.

Genetic load

mutation loadGenetic entropymutational load
Haldane's dilemma regarding the cost of selection was used as motivation by Kimura.
Motoo Kimura's original argument for the neutral theory of molecular evolution was that if most differences between species were adaptive, this would exceed the speed limit to adaptation set by the substitutional load.

Molecular clock

molecular clock hypothesismolecular clocksmolecular dating
This provides a rationale for the molecular clock - which predated neutral theory.
Later, the work of Motoo Kimura developed the neutral theory of molecular evolution, which predicted a molecular clock.

Molecular evolution

chemical evolutionprotein evolutionevolution
Selectionists claimed that polymorphisms are maintained by balancing selection, while neutralists view the variation of a protein as a transient phase of molecular evolution.
In the late 1960s, the neutral theory of molecular evolution provided a theoretical basis for the molecular clock, though both the clock and the neutral theory were controversial, since most evolutionary biologists held strongly to panselectionism, with natural selection as the only important cause of evolutionary change.

Mutation

mutationsgenetic mutationmutated
The neutral theory of molecular evolution holds that most evolutionary changes at the molecular level, and most of the variation within and between species are due to random genetic drift of mutant alleles that are selectively neutral.

Synonymous substitution

synonymoussynonymous mutationssynonymous mutation
Consequently, many potential single-nucleotide changes are in effect "silent" or "unexpressed" (see synonymous or silent substitution).
When a synonymous or silent mutation occurs, the change is often assumed to be neutral, meaning that it does not affect the fitness of the individual carrying the new gene to survive and reproduce.

Adaptive evolution in the human genome

adaptive evolutionheritable
The methods used to identify adaptive evolution are generally devised to test the null hypothesis of neutral evolution, which, if rejected, provides evidence of adaptive evolution.

Masatoshi Nei

Neibirth-and-death
He has also developed concepts in evolutionary theory and advanced the theory of mutation-driven evolution.

Codon degeneracy

degeneracydegenerate genetic codeCodon redundancy
This view is based in part on the degenerate genetic code, in which sequences of three nucleotides (codons) may differ and yet encode the same amino acid (GCC and GCA both encode alanine, for example).
*Neutral theory of molecular evolution

Gene

genesnumber of genesgene sequence
According to ISM, selectively neutral mutations appear at rate μ in each of the 2N copies of a gene, and fix with probability 1/(2N).
Most changes to a gene's sequence do not affect its function and so genes accumulate mutations over time by neutral molecular evolution.

Genetic hitchhiking

hitchhikergenetic draftgenetic hitch-hiking
This stochastic process is assumed to obey equations describing random genetic drift by means of accidents of sampling, rather than for example genetic hitchhiking of a neutral allele due to genetic linkage with non-neutral alleles.
The neutral theory of molecular evolution assumes that most new mutations are either deleterious (and quickly purged by selection) or else neutral, with very few being adaptive.

Effective population size

effective populationbreeding populationeffective population sizes.
According to the neutral theory of molecular evolution, the amount of genetic variation within a species should be proportional to the effective population size.
According to the neutral theory of molecular evolution, a neutral allele remains in a population for Ne generations, where Ne is the effective population size.

Coalescent theory

coalescencecoalescentcoalesce
Coalescent theory is a natural extension of the more classical population genetics concept of neutral evolution and is an approximation to the Fisher–Wright (or Wright–Fisher) model for large populations.

Unified neutral theory of biodiversity

neutral theoryunified neutral theory of biodiversity and biogeographyneutral model
Hubbell calls this simplified model for speciation a point mutation, using the terminology of the Neutral theory of molecular evolution.