Which sequence feature of a prokaryotic transcription unit best predicts rho-independent termination?
- A A purine-rich stretch followed by an AT-rich region
- B An inverted GC-rich repeat followed by a run of adenines on the template strand ✓
- C A conserved heptamer-spacer-nonamer motif recognised by rho protein
- D A TATAAT box located 10 bases downstream of the coding region
Correct answer: B. An inverted GC-rich repeat followed by a run of adenines on the template strand
Explanation
Rho-independent termination depends on a palindromic GC-rich inverted repeat that forms a stable hairpin in the nascent RNA, followed by a poly-U sequence transcribed from adenines in the template. The weak rU-dA pairing plus the hairpin destabilises the elongation complex and releases the transcript. Rho-dependent termination instead uses unstructured rut sites and ATP-driven rho helicase, and the -10 TATAAT box functions in initiation, not termination.
Reference: Lewin's Genes, 12th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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