What happens if RNA polymerase makes an error during transcription?

Errors in transcription can have harmful consequences, especially when mRNA containing mistakes is repeatedly translated into proteins. These errors may contribute to aging and various human diseases, including cancer. 

To maintain accuracy, RNA polymerase II (Pol II) can recognize mis-incorporated RNA and correct errors to ensure that each messenger RNA matches the template DNA. The impact of mistakes made by RNA polymerase varies depending on their location within the mRNA sequence. Errors occurring in critical regions of the mRNA may affect the overall editing process, potentially leading to significant alterations in the final protein product. In contrast, errors in other regions may result in minor changes to the encoded protein.