Step 1: Initiation

  • DNA double helix is unzipped by DNA helicase.
  • The separation of the DNA strands creates a ‘Y’ shape replication ‘fork’.
  • These two separated strands will act as templates for making new DNA strand.
  • The leading strand is oriented in the 3’ to 5’ direction (towards the replication fork).
  • The lagging strand is oriented in the 5’ to 3’ direction (away from the replication fork).
  • As a result of their different orientations, the two strands are replicated differently.