DNA Replication 2(1)
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Transcript of DNA Replication 2(1)
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ENZYME: DNA-directed DNA polymerase
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DNA RNA Protein
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1. Semi-conservative2. Ordered and sequential3. Uses activated substrates4. Semi-discontinuous5. Accurate
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1. Initiation2. Elongation3. Termination
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A circular bacterial chromosome has a single origin of replication.
oriC : origin of replication of E. coli
1. Recognition of origin of replication by specific proteins
2. Formation of replication fork
INITIATION: Prokaryotic DNA Replication
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Dna A – for identification of origin of replication
DNA Helicase – unwinds the DNA
Single strand DNA binding protein – prevents the reannealing of DNA
INITIATION: Prokaryotic DNA Replication
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1. Both strands of the DNA double helix must be copied. DNA polymerase has only 5’ 3’ polymerase activity.
2. DNA polymerase cannot initiate DNA synthesis on a molecule that is entirely single-stranded.
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ELONGATION: Prokaryotic DNA Replication
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ELONGATION: Prokaryotic DNA Replication
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1. Excision of RNA primers by DNA polymerase I
2. Filling up of the gaps by DNA polymerase I
3. Nick ligation
ELONGATION: Prokaryotic DNA Replication
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DNA polymerase has DNA polymerase has proofreading abilityproofreading ability
DNA polymerase IIIDNA polymerase III3’ 5’ exonuclease activity
DNA polymerase IDNA polymerase I3’ 5’ exonuclease activity5’ 3’ exonuclease activity