Act I: Initiation
- Helicase unwinds the double-stranded DNA at locations called replication origins. The structure that is created is known as "replication fork".
- Single-strand-binding-proteins then help to stabilize the newly unwound single strand, and prevent it from rebinding with its other strand.
- As the DNA unwinds, tension starts to build up on either sides of the unwound strand. Gyrase then comes in and cuts the two ends to release the tension.
- An RNA primer is added on to the DNA template strands by the enzyme primase to initiate the DNA replication process.
Act II: Elongation
- DNA polymerase III starts adding new nucleotides to the end of the RNA primers to create a new DNA daughter strand complementary to the original strand.
- SInce DNA is antiparallel, the new strands will grow in the opposite direction of each other.
- Leading strand: synthesized continuously in the 5'->3' direction by polymerase III. Only one RNA primer is needed to initiate the replication.
- Lagging strand: synthesized discontinuously in the 3'->5' direction by polymerase III. In the lagging strand, the RNA primase adds many RNA primers to form short, discontinuous fragments known as Okazaki fragments.
Act III: Termination
- Polymerase I comes in and now proofreads the lagging strands and replaces the RNA primers with DNA nucleotides.
- As a polymerase III reaches a previous RNA coded section, the Okazaki segments are glues together with ligase.
'
