<P> De novo DNA synthesis is DNA replication without the need for precursor template DNA . It's also referred to as artificial gene synthesis . Primase is an RNA polymerase, and it can add a primer to an existing strand awaiting replication . DNA polymerase cannot add primers, and therefore, needs primase to add the primer de novo . </P> <P> De novo pathways do not use free bases: adenine (abbreviated as A), guanine (G), cytosine (C), thymine (T), or uracil (U). The purine ring is built up one atom or a few atoms at a time and attached to ribose throughout the process . Pyrimidine ring is synthesized as orotate and attached to ribose phosphate and later converted to common pyrimidine nucleotides . De novo synthesis enzymes are predicted to be present as large multienzyme complexes, although this hypothesis has yet to be thoroughly proven . </P>

In the de novo synthesis of dna and rna