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Chapter 1 - Basics of Replication

Chapter 1 - Basics of Replication - DNAReplication...

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Francis Crick and James Watson Review of the Basics of Bacterial  Chromosome Replication and Structure
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Polarity and Antiparallel Orientation of Strands in DNA
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3’ 5’ A B A B 3’ 5’ 3’ 5’ DNA Replication My Heroes In 1953 Watson and Crick  PREDICTED  that DNA  replication is  semi- conservative , meaning  that each strand can act  as a template for the  synthesis of its  complementary  strand by a process  that takes advantage of the rules of base  pairing:  two new copies are made, each  consisting of an “old” (template) strand  and a “new” strand. In 1958,  Matthew Messelson  and  Franklin  Stahl  confirmed experimentally that DNA  replication is semiconservative.
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Polymerization of Deoxyribonucleoside Triphosphates  (dNTPs) as dNMPs during DNA Synthesis The  β - γ  diphosphate (pyrophosphate) is cleaved to provide the  energy required for formation of a phosphoester bond by the  α   phosphate of the dNTP with the 3’ carbon at the end of a growing  DNA strand. Fig. 1.6 HO HO Some  corrections 
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  Protein Gene Function DnaA dnaA Initiator protein, primosome (priming complex) formation  DnaB dnaB DNA helicase (strand separation; hexamer) DnaC dnaC Delivers DnaB to replication complex SSB ssb Binding to single-stranded DNA  Primase dnaG RNA primer synthesis DNA Pol III 11 genes DNA replication (presented in next slide)   DNA Pol I polA Primer removal, gap filling DNA ligase lig Sealing DNA nicks DNA gyrase DNA   supercoiling (unwinding)     α  subunit gyrA   Nick closing        subunit β gyrB ATPase Topo I topA DNA supercoiling (DNA “packaging”)   Pol III TABLE 1.1 Proteins involved in  E. coli  DNA  replication
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a  Full-length translation product of  dnaX  gene b  Shorter product of  dnaX  gene produced by translational frameshifting (Chapter 2) Subunit Gene Function α dnaE   Polymerization (catalytic subunit). ε   dnaQ   3’   5’ editing exonuclease.   RNase H          rnhA Removes RNA primers? Endonuclease that  cleaves RNA in RNA/DNA duplexes. Primer  removal in eukaryotes. θ holE  Present in core.  β dnaN  Sliding clamp. τ a   dnaX   Organizes complex; joins leading and lagging  DNA PolIII  complexes.  γ b   dnaX   Clamp loading. δ   holA   Clamp loading. δ   holB   Clamp loading. χ   holC   Clamp loading. ψ   holD Clamp loading. TABLE 1.1 The  11  polypeptides of the  E. coli  DNA Pol III  (holoenzyme)
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A.  All DNA polymerases synthesize DNA strands from the 5’-end to the  3’-end.
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