Practice question

RNA dependent RNA polymerase synthesizes RNA polymer using RNA template, reaction central to life cycles of RNA viruses. Unlike DNA-dependent RNA polymerase transcribing DNA to RNA, RdRp reads single-stranded or double-stranded RNA via complementary base pairing producing new RNA strand. Active site contains conserved GDD motif coordinating magnesium ions catalyzing phosphodiester formation. Host mammalian cells generally lack RdRp except for limited RNA interference amplification pathways, whereas most RNA viruses encode own enzyme for replication. Enzymatic activity often membrane-associated, lacking proofreading, contributing to high mutation rates among RNA viral genomes during propagation.