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( Molecular clock)
Adaptation
Genetic drift
Gene flow
Mutation
Natural selection
Speciation The molecular clock (based on the molecular clock hypothesis (MCH)) is a technique in molecular evolution to relate the divergence time of two species diverged to the number of molecular differences measured between the species' DNA sequences or proteins. It is sometimes called a gene clock or evolutionary clock. The notion of the existence of a so-called "molecular clock" was first attributed to Emile Zuckerkandl and Linus Pauling who, in 1962, noticed that the number of amino acid differences in hemoglobin between lineages scales roughly with divergence times, as estimated from fossil evidence[1]. They generalized this observation to assert that the rate of evolutionary change of any specified protein was approximately constant over time and over different lineages. Later Allan Wilson and Vincent Sarich built upon this work and the work of Motoo Kimura observed and formalized that rare spontaneous errors in DNA replication cause the mutations that drive molecular evolution, and that the accumulation of evolutionarily "neutral" differences between two sequences could be used to measure time, if the error rate of DNA replication could be calibrated.[2][3] One method of calibrating the error rate was to use as references pairs of groups of living species whose date of speciation was already known from the fossil record.
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Molecular clock Subcategories
Molecular clock Articles
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