Practice question

Run-off transcription is an in vitro biochemical assay designed to study promoter strength and transcription factor requirements. A DNA template containing a promoter followed by a defined sequence is linearized downstream with restriction enzymes, causing RNA polymerase to transcribe and then fall off at the cut site, producing a transcript of fixed length. Reactions include labeled UTP and nuclear extracts or purified factors. Quantity of RNA synthesized is measured by autoradiography. Northern blot detects steady-state RNA, SAGE quantifies tags, and ChIP assesses protein occupancy, not transcription rate from truncated template.