Molecular Clock Hypothesis

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Molecular Clock Hypothesis

• Camille K. Sandlin
• EvolutionSpring 2005

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Molecular Clocks

• Depends on the particular protein and group of
  species being compared
• The rate of evolution of informational
  macromolecules is constant through time

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Kimuras Theory

• Motoo Kimura
• Neutral Theory of Molecular Evolution
• Based on theory by Zuckerkandl and Pauling
• New mutations 2Nu

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Evolutionary Changes

• Amino acid changes in a protein neutral
• Change has little/no effect on fitness of
  organism
• Rate of change not affected by natural selection
  (Sorry Darwin!)
• Neutral changes would accumulate and would only
  be influenced by the mutation rate CONSTANT

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Substitution Rates

• Rate of evolution of a gene or mutation under
  selection will be very different
• Different rates in different lineages of organisms

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Criticisms

• Various generation times
• Nucleotide
• Organisms
• DNA repair efficiency
• Mutagen exposure
• Number of DNA replications in germ line cells

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Universal Rate

• Many clocks ticking at same time
• The rate of molecular evolution is NOT constant
• Proven to be wrong by theory of natural selection
• Local Clock

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Ohtas Theory

• Generation Time Hypothesis
• Generation time vs. chronological time
• Nearly Neutral Theory of Evolution

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References

• Bayas, Marco. Rate of Molecular Evolution.
  October 31, 2001.
• Bromham, Lindell and David Penny. The Modern
  Molecular Clock. Nature Reviews Genetics.
  March 2003, Volume 4, pg. 216-224.
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• Covey, Jon and Anita K. Millen. The Molecular
  Clock Hypothesis. http//www.creationinthecrossfir
  e.com/Articles/
•  
• Hermann, Gilbert. Current Status of the Molecular
  Clock Hypothesis. The American Biology Teacher.
  Nov/December 2003, Volume 65, Issue 9, pg. 661.
•  
• Lecture 27 Molecular Clocks and the Estimation
  of Divergence Times. http//www.biology.usu.edu/b
  iol6750/Lecture_27.htm
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• Lewin, Roger. Molecular Clocks Turn a Quarter
  Century. Science. February 5, 1988, Volume 239,
  Issue 4840, pg. 561-63.
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• Molecular Evolution. http//biomed.brown.edu/Cours
  es/BIO48/12.Molecular.Evolution.HTML
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• The Molecular Clock Problem. http//www.cs.unc.edu
  /plaisted/ce/clock.html

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Congratulations!

• We finally made it! Good Luck at Graduation!