Molecular clock

In Genetic, the assumption of the molecular clock stipulates that the genetic mutations accumulate in a Génome at a speed overall proportional to geological time.

In 1962, Emile Zuckerkandl and Linus Pauling were the first to observe this phenomenon in the part of the Génome coding the Hémoglobine between two species given. The observation of such a constancy of the rate of evolution along the Phylogénie of the alive world was surprising, taking into account the variation of several factors being able to enter in account, such as the variation of generation or the variation time of the pressure of selection.

The reconciliation of the assumption of the molecular clock and the theory Darwinienne was started towards the end of the Années 1960 by work of Motoo Kimura, Allan Wilson and Vincent Sarich, and of the development of the uncommitted Théorie of the evolution. This one claims that the vast majority of the accumulated genetic mutations are neutral, i.e. they do not confer on the individual undergoing the change a marked selective advantage.

The molecular clock made it possible many researchers to date from the events of speciations using phylogenetic methods increasingly developed. However, whereas the quantity of genetic data increased and that the statistical methods were refined, it became increasingly clear at least that the molecular clock was not valid, in certain parts of the Phylogénie of the living beings. Since, several models were proposed in order to soften the molecular clock by sophisitiqués statistical models (Maximum of probability, methods bayésiennes), said released molecular clock . These models have the advantage of giving times of divergence between more precise species, and more in agreement with the paleontological data.

See too

Genetic Evolution
Phylogenetic tree
of the populations
molecular Phylogeny

External bonds

The Neutral Theory off Molecular Evolution
Allan Wilson and the molecular clock

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