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Mitochondrial Point Mutations and Evolution: A Comparative Study

Mitochondrial Point Mutations and Evolution: A Comparative Study. Plethodon stormi. Plethodon elongatus. Stephanie Weitz Mentor: Dr. Dee Denver Department of Zoology. Plethodon asupak. <http://www.californiaherps.com/salamanders/images>. General Background on Western Plethodons .

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Mitochondrial Point Mutations and Evolution: A Comparative Study

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  1. Mitochondrial Point Mutations and Evolution: A Comparative Study Plethodon stormi Plethodon elongatus Stephanie Weitz Mentor: Dr. Dee Denver Department of Zoology Plethodon asupak <http://www.californiaherps.com/salamanders/images>

  2. General Background on Western Plethodons • Important distinction between three species is range: • P. elongatus has large range in SW Oregon and NW California • P. stormi is restricted to small pockets in Siskiyou mountains of California • P. asupak is found a few miles west of P. stormi in the Siskiyous <http://www.bioone.org/perlserv/?request=display-figures&name=i0018-0831-61-2-158-f01>

  3. Darwinian Theory: Species adapt to environment by natural selection Neutral Theory of Molecular Evolution: Introduced by Motoo Kimura in the late 1960s At molecular level evolution occurs via random drift of neutral mutations Foundation of molecular clock hypothesis Evolution http://www.biology-blog.com/images/blogs/12-2007/charles-darwin-8221.jpg http://www.philo5.com/images/VraisPenseurs/KimuraMotoo200.jpg

  4. The mitochondrial genomes of these three Plethodons have large amounts of non-coding sequences that experience faster rates of evolution than protein-coding sequences. www.ccc.columbia.edu/Mitochondrial_Diseases/mito/round Hypothesis Muller et al. 2006

  5. Objectives 1. Compare rates of evolution between three species using three different measures 2. Use rates to calculate time to the most recent common ancestor between species <http://www.californiaherps.com/salamanders/pages/p.asupak.html>

  6. Methods DNA extraction Designed primers Obtained tissue samples Perform DNA sequence alignments MtDNA sequencing PCR-amplify Data analysis in MEGA 4.1 and DNAsp 4.1

  7. Measuring Rates of Evolution • Ka: rate of substitution at amino acid-changing (replacement) codon positions • Ks: rate of substitution at silent codon positions • Knc: rate of substitution at any site in non-coding regions http://evolution.berkeley.edu/evosite/evo101/images/codon_GCA.gif http://www.mun.ca/biology/scarr/MGA2-03-28_mtDNA_code.jpg

  8. Molecular Clock Equation • TMRCA=Time to the most recent common ancestor (millions of years) • K= Rate of evolution (Ka, Ks, Knc) • µ= Mutation rate (humans=.95/base pair/Million year) • Assumptions necessary to use equation

  9. Data • Not all primers worked in all species • P. asupak: only half of the primers worked • Used pairwise DNA sequence alignments to calculate Ka, Ks, Knc

  10. Objective I Results • Highest rates of evolution occurred at silent sites • Lowest rates of evolution occurred at replacement sites • Rate of evolution intermediate for Knc

  11. Objective II Results • Ka and Knc give comparable, more recent times • P. elongatus and P. stormi are the most closely related • P. stormi and P. asupak are the most distantly related

  12. Conclusion • Highest rate of evolution occurred at silent sites • P. elongatus and P. stormi are the most closely related. P. stormi and P. asupak are the most distantly related • Speciation occurred 250,000 years ago

  13. Future Research • Amplify entire mitochondrial genomes for all three species • Find divergence times within species

  14. Acknowledgements • Denver lab: Dee, Dana, Sam, Caroline, Ashley, Bobby, Peter, Larry • Dr. Kevin Ahern • HHMI • Albert Lee, PharmD Candidate 2010 • Dr. Stevan Arnold and Douglas DeGross

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