In prokaryotic transcription, termination can occur via two mechanisms: rho-independent (intrinsic) and rho-dependent. Which structural feature is characteristic of rho-independent termination?

• A A rut site on the nascent RNA to which rho factor binds
• B A stem-loop structure followed by a poly-A tract in the RNA
• C An ATP-dependent helicase that dissociates the RNA-DNA hybrid
• D A GC-rich palindrome followed by a poly-U tract in the RNA ✓

Explanation

Rho-independent termination relies on a GC-rich inverted repeat in the DNA that forms a stable hairpin (stem-loop) in the RNA, followed by a stretch of uracils. The hairpin destabilizes the RNA polymerase's interaction with the DNA, and the weak rU-dA base pairing facilitates release. Rho-dependent termination requires the rho factor binding to the rut site and ATP hydrolysis, making option A describe the rho-dependent mechanism.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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