DNA Replication - Step by Step

Step 1: Initiation

Helicase unwinds the DNA double helix at the origin of replication, creating a replication fork.

5'---========---3' → 5'---[Helicase]---3'
3'---========---5' 3'---[breaks]---5'

Step 2: Primer Synthesis

Primase synthesizes short RNA primers on each strand to initiate DNA synthesis.

5'---[RNA Primer]---3'
3'---[RNA Primer]---5'

Step 3: DNA Synthesis

DNA Polymerase III extends from the RNA primers, adding nucleotides (A, T, G, C) to synthesize new DNA strands.

5'---[RNA][ATGCATGC]---3'
3'---[RNA][TAGCTACG]---5'

Step 4: Primer Removal

DNA Polymerase I removes RNA primers and fills gaps with DNA nucleotides.

Step 5: Ligation

DNA Ligase seals the breaks in the DNA backbone, creating complete double-stranded DNA molecules.

5'---[DNA Ligase]---3'
3'---[creates bonds]---5'