RNA polymerase

RNA polymerase is an enzyme that catalyzes transcription and produces RNA. Bacteria have a single type of RNA polymerase whereas eukaryotic nuclei have three, RNA polymerase I, RNA polymerase II and RNA polymerase III. It unwinds the DNA for complementary base-pairing in the 5' - 3' direction (downstream). The nucleotides for base-pairing are UTP, ATP, GTP and CTP. The hydrolysis of the nucleotide triphosphate bonds gives energy for transcription to move forward. Unlike DNA replication, transcription doesn't require RNA primers. However, RNA polymerase make about one mistake per 10⁴ nucleotides, whereas DNA polymerase only makes about one mistake per 10⁷ nucleotides , this is due to RNA polymerase having no proof-reading function, unlike DNA polymerase.