Dna replication involves several steps. first, the enzyme, helicase, unwinds the hydrogen bonds of the dna double helix. then dna polymerase attaches the complementary nucleotides thereby creating two semi-conservative strand of identical dna. semi-conservative replication of dna refers to the idea that dna molecules need to unwind before duplication can begin. each new dna molecule contains two new single rna strands. the identical two strands of dna molecules run in opposite directions. two identical dna strands contain part old and now part new nucleotides.