DNA Replication
Base pairing allows each strand to serve as a template for a new strand. The new strand is half parent template and half new DNA. This is known as semi-conservative replication.
Stage 1: Unwind DNA
Done by a helicase enzyme
Breaks the hydrogen bonds between the bases
This unwinds part of DNA helix, allowing the separation of the strands.
Stage 2: Build daughter DNA strand
Add new complementary bases.
Done by the enzyme, DNA polymerase.
The enzyme moves 3′ to 5′ and can only add nucleotides to the 3′ end of a growing DNA strand.
Therefore the strand will grow 5′ → 3′.