Describe the process in which DNA replication occurs (6 marks)

Firstly, the enzyme DNA helicase separates the two strands in DNA by breaking the hydrogen bonds between them. Both of the two strands then act as templates to which free nucleotides attach to. This attachment occurs by complementary base pairing, where cytosine and guanine bases join, and adenine and thymine bases join. The enzyme DNA polymerase then moves up the new strands, joining the nucleotides on them with phosphodiester bonds. The hydrogen bonds between bases reform, and the DNA has successfully replicated by semi-conservative replication.