1) Initiation
- Helicase - unwinds the double stranded DNA helix
- Single-Strand Binding Proteins - react with single stranded DNA to stabilize it and keep the DNA strands separated
- Gyrase - relieves tension in the DNA from unwinding process
- Primase (RNA Polymerase)
- creates RNA primers (~10 primers; according to parent strand)
- initiates Polymerase III to form complementary strand
2) Elongation
- DNA Polymerase III - attaches to a primer and adds nucleotides to 3' end of the new DNA strand
- 2 types of strands in each strand:
- Leading Strand - from 5' --> 3' into replication fork
- Lagging Strand - from 5' --> 3' away from replication fork; replicates in short segments (Okazaki Fragments) - DNA Polymerase I - replaces Polymerase III when it reaches the primer and replaces the RNA primer with correct DNA sequence
3) Termination
- DNA ligase
- attaches and forms phosphodiester bonds
- connects Okazaki Fragments
Note:
- semi-conservative - one parent strand & one daughter strand in the replicated DNA
- new DNA strand can only elongate in the 5' --> 3' direction
