DNA Replication

The Process of DNA Replication:
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