How does DNA undergo replication?

Firstly, the enzyme DNA Helicase breaks the hydrogen bonds present between base pairs. This allows the DNA double helix to unravel, exposing the DNA bases. Free DNA nucleotides then bond to the exposed base pairs according to complementary base pairing (adenine with thymine, guanine with cytosine and vice versa). Both DNA strands act as a template. The enzyme DNA Polymerase then moves along the new DNA strand, forming phosphodiester bonds between adjacent DNA nucleotides in condensation reactions. A condensation reaction is one in which water is a product. DNA replication is semi-conservative because each new DNA double helix contains one old strand and one new strand.