The analysis of published data from E coli suggests that in all three processes of translation, transcription, and replication, a minority of errors are produced by sub-classes of error-prone components. These add to the basal level of errors a noise of about 10 to 30%. Each one of the three processes contributes to the noisiness of the two others in a loose manner: a large increase in one error-rate produces a moderate increase in another error-rate. The strongest influence is that of transcription on translation errors. There it is possible that a majority of the misacylation errors are produced during the encounter of a correct amino acyl-tRNA ligase with a mistranscribed tRNA. Extreme mutator mutants are expected to produce a moderate increase in translation errors.