What is the error rate of RNA polymerase?

RNA polymerase has a very high error rate. This stems from its lack of proofreading activity, which prevents it from being able to correct any mistakes made during transcription.

The error rate of RNA polymerase is about 1 per 100,000 nucleotides. This may seem like a marginal rate until you consider the amount of DNA in each cell. For example, humans have six billion pairs of DNA in each diploid cell. With an approximate error rate of 1 per 100,000 nucleotides, this could add up to potentially 120,000 mistakes every time a cell divides.