Practice question

In run-off transcription assays, a linear DNA template is incubated with RNA polymerase and radiolabeled or fluorescently tagged ribonucleotides. Transcription proceeds to the end of template, generating transcripts of uniform length dictated by restriction cut position. These products are electrophoresed on denaturing polyacrylamide gels and detected by autoradiography. Band intensity correlates proportionally with the number of transcription events and overall transcriptional activity under experimental condition, reflecting promoter efficiency, factor presence, or inhibitor effect. It does not report DNA purity, mRNA degradation, or RNase activity directly.