In vitro transcription assays are performed with radioactive nucleotide triphosphates and the amount of radioacivity incorporated is measured by separating the unincorporated nucleotides from the ones incorporated into rna by counting in a scintillation counter. the results are recorded as counts per minute or cpm. in this experiment a series of different inhibitors are added 10 minutes after the reactions have been started and the transcription reactions allowed to proceed for the indicated times. use the labels to indicate what the expected results would be for the different conditions.