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Molecular Genetics Chapter 4

Molecular Genetics Chapter 4. Self-Study. Read sections 4.1 and 4.2 on your own . You will be responsible for knowing a few of the experiments, which led to the discovery of location of Hereditary Material and DNA Structure . Suggested Questions: Pg. 216 #1-6 and 10. .

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Molecular Genetics Chapter 4

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  1. Molecular GeneticsChapter 4

  2. Self-Study • Read sections 4.1 and 4.2 on your own. You will be responsible for knowing a few of the experiments, which led to the discovery of location of Hereditary Material and DNA Structure. • Suggested Questions: Pg. 216 #1-6 and 10.

  3. Example– summarize each experiment and significance

  4. 4.3 DNA Replication and Repair

  5. How does DNA replicate? • Meselson and Stahl determined a Semiconservative Model • Means that a replicated DNA molecule is composed of one parent strand and one newly synthesized strand • Experiment used radioactively labeled DNA from E.coli

  6. DNA Replication III

  7. 3’ 5’ RNA Primer 3’ 5’ Direction of unwinding 3’ RNA Primer Primer 5’ 5’ 3’ 3’ 5’ Leading and Lagging Strands Leading Strand Reads template 3’5’ Builds new strand 5’3’ LaggingStrand

  8. Enzymes Acting During New DNA Strand Synthesis: • DNA Helicase – unzipping • DNA Gyrase – reduce tension of unwinding • SSB’s – help keep strands apart • DNA Polymerase III – adds nucleotides to create new strand (complimentary base pairing) • DNA Primase – lays down RNA primer (“temporary” 6-10bp) Acting After Elongation of New DNA Strand: • DNA Polymerase I – replaces RNA primer and proofreading • DNA Ligase – joins gaps between okazaki fragments

  9. How It Happens Reads template 3’5’ DNA helicase http://www.youtube.com/watch?v=teV62zrm2P0

  10. Mechanism for Incorporating New Nucleotides • DNA Polymerase III adds free Dioxyribonucleoside triphosphate(dNTP) • Always added to the 3’-OH end (since new strand builds in 5” 3’ direction) • Bond breaks between first two phosphates to drive process of elongating the strand (2p recycled to make more dNTP) 3 Phosphates Deoxyribose

  11. Mechanism for Incorporating New Nucleotides

  12. Key Points to Know: • Each parent strand acts as a template (semiconservative model) • Reads DNA template 3’5’ and Builds 5’3’ • Mechanism for joining dNTP’s • Know which is your Leading strand (towards fork) and Lagging strand (away from fork) • Know all acting enzymes and proofreading process

  13. Try Some Questions • Pg. 223 Q# 1,2,5 • Pg. 230 Q# 4,6,7 • Handout– will help quiz and review steps • “Awareness Presentation” (due Dec19th) More realistic animation of DNA replication http://www.youtube.com/watch?v=4jtmOZaIvS0&feature=related

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