Now another important distinction that must be known between DNA polymerase and RNA polymerase is the following. DNA polymerase has the ability to basically correct any mismatches that are made with our base pairs. However, RNA does not have this proofreading mechanism and that means many more errors are actually formed during the process of transcription than the process of replication. And that makes sense because during replication we have to replicate our DNA precisely to pass it down to our offspring. Now the other thing that I want to mention about RNA polymerase is the following. In prokaryotic organisms there's only one RNA polymerase while in eukaryotic organisms there are three different types of RNA polymerases and each one of these RNA polymerases is used to synthesize the three different types of RNA molecules our messenger RNA, the transfer RNA and the ribosomal RNA.