So RNA polymerase catalyzes the initiation and the elongation of that RNA polynucleotide chain. And to see what we mean by that, let's take a look at the following diagram. So in the diagram in this chemical equation we basically describe how this reaction takes place and what RNA polymerase does. So let's suppose we have an RNA chain and we're extending that RNA chain. So we're building our RNA molecule. Now, so far in our RNA molecule we have N number of nucleotides.