MBIO exam 3 notes

MBIO exam 3 notes - Bidirectional Replication = chromosome replicated in half the time Unidirectional Replication = some plasmids(smaller organisms

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10/29/2009 Bidirectional Replication = chromosome replicated in half the time Unidirectional Replication = some plasmids (smaller organisms) Replication fork proceeds (moves forward) at ~ 1000 base pairs per second E. coli : 4.6 x 10 6 bp = 4.6 x 10 6 bp / 2 replication forks = 2.3 x 10 6 bp per replication fork / 1000 bp per second = 2.3 x 10 6 sec / 60 sec per min = ~ 40 mins (to replicate an E. coli chromosome) Isolating mutants Conditional-lethal mutants DNA Polymerases: 1. Pol A = DNA Polymerase I 2. Pol B = DNA Polymerase II 3. DNA Polymerase III 10 different subunits Core replication enzyme DNA Polymerase III Subunits (10): Core Complex (DNA Synthesis and Editing): 1. α (alpha) polC (dnaE) 2. ε (epsilon) dnaQ (mutD) 3. θ (theta) holE Clamp (Processivity): 4. β ( beta) dnaN Gamma Complex (Clamp Loader): 5. γ (gamma) dnaX (dnaZ) 6. δ (delta) holA 7. δ (delta prime) holB 8. χ (chi) holC 9. ψ (psi) holD
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Linker Protein: 10. τ (tau) dnaX (dnaZ) Activities of DNA Polymerase: 1. ALL DNA polymerases require a template for synthesis of a new complementary strand 2. ALL DNA polymerases require a primer DNA Polymerases I-III: 1. ALL have 5’ 3’ primer extension activity 2. ALL have 3’ 5’ exonuclease activity 3. DNA pol. I and III (NOT II) have 5’ 3’ exonuclease activity (repair activity) Semiconservative Replication Okazaki Fragments = Relatively short fragments of DNA synthesized on the lagging strand during DNA replication Events at the Replication Fork: 1. Unwind double-stranded DNA = DNA Helicase (DNA B) 2. Single-Stranded DNA Binding Protein = protein stabilizes unwound strands (Ssb ) 3. Synthesize Primers : Primase = (DNA G ) 4. DNA Polymerase III extends the primer in the 5’ 3’ direction 5. Remove RNA primers and replace with DNA = DNA Polymerase I (Pol A) 6. Join Okazaki fragments = DNA Ligase (Lig) Continuous vs. Noncontiuous DNA Synthesis: Okazaki fragments coordinate synthesis of both DNA strands Stationary DNA, moving replication forks (Track Model ) Stationary replication forks, moving DNA (Factory Model )
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( Bacillus = favors Factory Model) DNA Replication: 3 Stages: 1. Initiation 2. Elongation (what happens at the replication fork) 3. Termination Initiation of DNA Replication: DNA A, DNA B , and DNA C (3 crucial proteins) o DNA B = DNA Helicase (crucial enzyme that begins unwinding process
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This note was uploaded on 04/29/2010 for the course MBIO 4404 taught by Professor Moss during the Fall '10 term at Texas Tech.

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MBIO exam 3 notes - Bidirectional Replication = chromosome replicated in half the time Unidirectional Replication = some plasmids(smaller organisms

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