Lecture 14 evo-devo evoln

Lecture 14 evo-devo evoln - Evolution in the News...

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“The majority of amino acid substitutions are not likely to provide either an evolutionary advantage or disadvantage and are preserved by sheer chance.” The Neutral Theory
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Parts of proteins that are indispensable to function will be very well preserved (that is, they will only rarely undergo mutation). Dispensable portions will have many more mutations.
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Kimura and Ohta's recognition of the neutral value of most mutations allowed the estimation of divergence times between related species by analyzing accumulated gene changes; the so-called molecular clock .
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Molecular Clocks Over the course of millions of years, mutations may build up in any given stretch of DNA at a reliable rate. The gene that codes for the protein α-globin (a component of hemoglobin) experiences base changes at a rate of 0.56 changes per base pair per billion years*. If this rate is reliable, the gene could be used as a molecular clock.
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Imagine that a length of DNA found in two species differs by four bases and we know that this entire length of DNA changes at a rate of approximately one base per 25 million years. The two DNA versions differ by 100 million years of evolution and their common ancestor lived 50 million years ago. Since each lineage experienced its own evolution, the two species must have descended from a common ancestor that lived at least 50 million years ago.
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Molecular Clocks http://evolution.berkeley.edu/evosite/evo101/IIE1cMolecularclocks.shtml#
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Phylogeny based on differences in the protein sequence of cytochrome c in organisms ranging from Neurospora mold to humans.
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This note was uploaded on 03/19/2008 for the course BIOL 101 taught by Professor Annestork during the Fall '08 term at Ithaca College.

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Lecture 14 evo-devo evoln - Evolution in the News...

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