An enzyme called DNA helices breaks the hydrogen bonds between the bases on two polynucleotide strands of DNA, forming two single strands. Each original strand acts as a template for a new strand. Complementary base pairing sees free floating DNA nucleotides being attracted to their complementary exposed DNA bases on each original strand. Adenine (A) binds with Thymine (T). Cytosine (C) binds with Guanine (G). Condensation reactions join the nucleotides of the new strand together, catalysed by the enzyme DNA polymerase. Hydrogen bonds form between the new bases on the original and new strands. Each new DNA molecule contains one strand from the original DNA strand and one new strand. This process is also known as semi-conservative replication.