what is actually an RNA polymerase?
RNA polymerase is the enzyme that assembles the individual nucleotides to create the RNA strand based on the DNA template. The RNA that is built here can actually be one of three different kinds. You may recall that the three different RNA types are mRNA, rRNA and tRNA. The type that we're concerned with here is mRNA.ere, initiation is the first phase of transcription, during which RNA polymerase attaches to the promoter and begins to build mRNA. The promoter for our keratin gene only exists on one strand of the DNA, which is how we know which strand is the antisense strand.