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Bio 178 Lecture 28

Bio 178 Lecture 28. DNA and Gene Expression. Reading. Chapters 14 & 15. ?. Quiz Material. Questions on P 300 & 318 Chapters 14 & 15 Quizzes on Text Website (www.mhhe.com/raven7). DNA DNA Replication Gene Expression Central Dogma Major Players Genetic Code

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Bio 178 Lecture 28

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  1. Bio 178 Lecture 28 DNA and Gene Expression

  2. Reading • Chapters 14 & 15 ? Quiz Material • Questions on P 300 & 318 • Chapters 14 & 15 Quizzes on Text Website (www.mhhe.com/raven7)

  3. DNA • DNA Replication • Gene Expression • Central Dogma • Major Players • Genetic Code • Transcription Outline

  4. Hershey and Chase Experiment McGraw- Hill Video

  5. How Does DNA Replicate? Complementarity suggested a copying mechanism. Eg. 5´-ACGTAAT-3´ pairs with 3´-TGCATTA-5´ There were 3 hypotheses: Conservative, dispersive, & semiconservative. • Meselson and Stahl (1958) The semiconservative hypothesis is correct. Read P 288-289 & predict what results would have been obtained for the other hypotheses (hand this in also).

  6. Meselson-Stahl Experiment

  7. Meselson-Stahl Results

  8. Meselson And Stahl Experiment McGraw-Hill Video

  9. The Replication Process (E. coli) • DNA Polymerases Enzymes that synthesize DNA: (a) Require a primer. (b) Can only synthesize in the 5´ to 3´ direction (copy a template that is 3´ to 5´). (c) Have nuclease activity, including 3´ to 5´ exonuclease activity (proofreading). • Leading and Lagging Strands Leading strand - synthesized continuously (5´ to 3´). Lagging strand - synthesized discontinuously (5´ to 3´ stretches (Okazaki fragments) as the DNA opens up, with filling in afterwards).

  10. Addition of DNA Nucleotides

  11. Leading and Lagging Strands

  12. The Replication Process (Cntd.) DNA Pol III is the main polymerase. • Some of the “Other” Enzymatic Activities 1. DNA Helicase Opens the DNA in front of polymerase. 2. DNA Primase Synthesizes primers (RNA). 3. DNA pol I Removes the primers (*5 ´ to 3´ exonuclease) and replaces them with DNA. 4. DNA Ligase Ligates Okazaki fragments (phosphodiester bond).

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