DNA Replication

1. Initiation

• Helicase unwinds the DNA and starts separating the strands.
• Single-Strand Binding proteins hold the strands in place and prevent them from coming back together
• Gryase cuts the DNA into smaller parts to prevent the tension from building up
• Primase place RNA Primers to signal Polymerase III to start making the replicated strand.

2. Elongation

• Polymerase III creates the replicated strand in the 5' to 3' direction.
  • The leading strand is done continuously (it is being unzipped in the 3' to 5' direction so the new strand can be created in the 5' to 3' direction without any breaks
  • The 'lagging' strand needs to be replicated in the opposite direction so it is done in sections called Okazaki Fragments.
• RNA Primase starts off each Okazaki Fragment and Polymerase III follows. Each Okazaki Fragment is approximately 100-200 nucleotides long

3. Termination

• Polymerase I 'proofreads' the replicated strand and corrects any errors. It also removes the RNA Primers and replaces them with Deoxyribonucleotides.
• Ligase forms Phosphodiester bonds between the Okazaki Fragments to hold them together.