Correct option is D
Explanation-
Option a - "Some terminator sequences require Rho protein for termination." - CORRECT
This describes Rho-dependent termination, a well-established mechanism in bacteria. Rho is a helicase that helps in terminating transcription at certain sites.
Option b - "Inverted repeat and 'T' rich non-template strand define intrinsic terminators." - CORRECT
This describes intrinsic (Rho-independent) termination correctly. These sequences form a hairpin loop in the RNA followed by a U-rich region, leading to polymerase dissociation.
Option c - "Rho-dependent terminators may possess inverted repeat elements." - CORRECT
Though not essential, inverted repeats may be present even in Rho-dependent terminators, but they are not a defining feature. Still, this statement is not false.
Option d - "Nus A is necessary for intrinsic transcription termination." - INCORRECT
This is the incorrect statement and thus the correct answer to the question. While Nus A may enhance intrinsic termination efficiency by stabilizing the hairpin loop structure, it is not strictly necessary. Intrinsic termination primarily depends on the RNA sequence itself (inverted repeats + U-rich region), not on protein factors like Nus A.
Since option d is the only incorrect option among all the other options that makes it a correct answer.
