Transcription: Elongation

Elongation is just the polymerase laying down bases, complementary to the template strand it is “reading” off of.  To transit from initiation from elongation, sigma factor is ejected (the purpose of sigma is to make the area sticky for RNA polymerase; now that polymerase has to go forward, sigma must be ejected so that RNA polymerase can move.

This diagram just shows the chemistry behind nucleic acid polymerization.  Polymerase brings in a nucleotide triphosphate (NTP) that is complementary to the base currently viewed on the template strand; once this is done, there is a concerted reaction where the phosphorus anhydride bond between the first and second phosphates are broken on the NTP, and a new bond between that first phosphate and the preceding nucleotide’s 3’ hydroxyl group is formed.