DNA replication is the process by which DNA makes a copy of itself during cell division. The first step in DNA replication is to ‘unzip’ the double helix structure of the DNA? molecule.This is carried out by an enzyme? called helicase which breaks the hydrogen bonds? holding the complementary? bases? of DNA together (A with T, C with G).The separation of the two single strands of DNA creates a ‘Y’ shape called a replication ‘fork’. The two separated strands will act as templates for making the new strands of DNA.