RNA polymerase establishes phosphodiester bonds between adjacent ribonucleotides held over DNA template to form RNA chain. As the RNA chain formation initiates, the sigma factor of the RNA polymerase separates.
Core enzyme of RNA polymerase moves along the DNA chain at the rate of some 30 nucleotides per second. The first nucleotide incorporated is always A or G. RNA synthesis stops as soon as core enzyme reaches the terminator region. Rho factor is required for this.
Terminator region has a stop signal and also possesses poly A base sequence (4 to 8 A –nucleotides) or palindromic sequence. RNA chain formation also requires a divalent ion Mg++. The released energy joins the ribonuclotides arrive earlier, making the RNA chain longer.