RNA Polymerase Role in Transcription — NEET Biology
✅ Asked in NEET 2024Given below are two statements: Statement I: In prokaryotes, RNA polymerase is capable of catalysing the process of elongation during transcription. Statement II: RNA polymerase associates transiently with 'Rho' factor to initiate transcription.
Given below are two statements: Statement I: In prokaryotes, RNA polymerase is capable of catalysing the process of elongation during transcription. Statement II: RNA polymerase associates transiently with 'Rho' factor to initiate transcription.
Identify the correct statement: (NEET 2021)
Answer & NCERT explanation
Correct answer: A — Statement I is True but Statement II is False
Statement I is true - RNA polymerase catalyzes elongation during transcription by adding ribonucleotides. Statement II is false - Rho factor helps in transcription termination, not initiation. RNA polymerase associates with sigma factor for initiation in prokaryotes. Rho-dependent termination occurs when Rho protein catches up to paused RNA polymerase and causes dissociation.
Read more NCERT concept on the PYQ
An intriguing question is that how is the RNA polymerases able to catalyse all the three steps, which are initiation, elongation and termination. The RNA polymerase is only capable of catalysing the process of elongation. It associates transiently with initiation-factor (σ) and termination-factor (ρ) to initiate and terminate the transcription, respectively. Association with these factors alter the specificity of the RNA polymerase to either initiate or terminate.
RNA polymerase itself can ONLY catalyze elongation (the middle step), not initiation or termination. It needs help from sigma (σ) factor to recognize promoters and start transcription, and from rho (ρ) factor to stop at terminators. Students commonly mistake RNA polymerase as doing all three steps independently—this is wrong. The key is understanding that factors temporarily associate with RNA polymerase to change its specificity. NTA tests this distinction because it's fundamental to transcription regulation and frequently appears in mechanism-based MCQs asking which factor does what.
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