text: RdRp differs from DNA dependent RNA polymerase as it works to catalyze the synthesis of an RNA strand complementary to a given RNA template, rather than using a DNA template. The RNA replication process is a four-step mechanism, as described.
  # Nucleoside triphosphate (NTP) binding – initially, the RdRp presents with a vacant active site in which an NTP binds, complementary to the corresponding nucleotide on the template strand. Correct NTP binding causes the RdRp to undergo a conformational change.
  # Active site closure – the conformational change, initiated by the correct NTP binding, results in the restriction of active site access and produces a catalytically competent state.
  # Phosphodiester bond formation – two Mg ions are present in the catalytically active state and arrange themselves in such a way around the newly synthesized RNA chain that the substrate NTP is able to undergo a phosphatidyl transfer and form a phosphodiester bond with the newly synthesized chain. Without the use of these Mg ions, the active site is no longer catalytically stable and the RdRp complex changes to an open conformation.
  # Translocation – once the active site is open, the RNA template strand is able to move by one position through the RdRp protein complex and continue chain elongation by binding a new NTP, unless otherwise specified by the template.
  RNA synthesis can be performed by means of a primer-independent (de novo) or a primer-dependent mechanism that utilizes a viral protein genome-linked (VPg) primer. The de novo initiation consists in the addition of a nucleoside triphosphate (NTP) to the 3'-OH of the first initiating NTP. During the following so-called elongation phase, this nucleotidyl transfer reaction is repeated with subsequent NTPs to generate the complementary RNA product. Termination of the nascent RNA chain produced by RdRp is not completely known, however, it has been shown that RdRp termination is sequence-independent.
  One major drawback of RNA-dependent RNA polymerase replication is the immense error rate during transcription.  RdRps are known to have a lack of fidelity on the order of 10 nucleotides, which is thought to be a direct result of its insufficient proofreading abilities. This high rate of variation is favored in viral genomes as it allows for the pathogen to overcome defenses developed by hosts trying to avoid infection allowing for evolutionary growth.