De novo synthesis
De novo synthesis refers to the synthesis of complex molecules from simple molecules such as sugars or amino acids, as opposed to recycling after partial degradation. For example, nucleotides are not needed in the diet as they can be constructed from small precursor molecules such as formate and aspartate. Methionine, on the other hand, is needed in the diet because while it can be degraded to and then regenerated from homocysteine, it cannot be synthesized de novo.
De novo is a Latin phrase, literally translating to "from the new," but implying "anew," "from scratch," or "from the beginning."
De novo DNA synthesis
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.
De novo pathways
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.