DNA Replication 2(1)

ENZYME: DNA-directed DNA polymerase

DNA RNA Protein

1. Semi-conservative2. Ordered and sequential3. Uses activated substrates4. Semi-discontinuous5. Accurate

1. Initiation2. Elongation3. Termination

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

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

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.

ELONGATION: Prokaryotic DNA Replication

ELONGATION: Prokaryotic DNA Replication

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

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