Practice question

Run-off transcription assay, also termed ROTA, measures rate and accuracy of transcription in vitro using defined linear DNA templates truncated at specific sites. RNA polymerase initiates at promoter and elongates until it reaches template end, where it runs off, producing transcript of predetermined length. Quantification of labeled runoff products by gel electrophoresis provides direct assessment of promoter strength and influence of transcription factors, activators, or inhibitors. It does not primarily measure mRNA decay, DNA synthesis, or DNA-protein binding affinity, which are addressed by northern blot, replication assays, or electrophoretic mobility shift assay respectively.