Q.68 The termination of transcription process in prokaryotes is carried out by:
A. Rho (ρ) independent mechanism
B. Ubiquitin pathway
C. Rho (ρ) dependent mechanism
D. Dicer
Choose the correct answer from the options given below:
- A, B and D only
- C and B only
- A and C only
- B and D only
A and C are the correct mechanisms for transcription termination in prokaryotes. Rho-independent termination involves a hairpin loop in the RNA followed by a poly-U tract that destabilizes the elongation complex, while Rho-dependent termination uses the Rho protein helicase to catch up and unwind the RNA-DNA hybrid.
B and D are incorrect, as the ubiquitin pathway handles eukaryotic protein degradation, and Dicer processes small RNAs like miRNAs in eukaryotes.
Correct Option: A and C only
Prokaryotic transcription termination Rho independent mechanism and Rho dependent mechanism are essential molecular biology concepts for competitive exams like GATE Life Sciences. This guide analyzes a multiple-choice question, explaining each option with scientific details to boost your understanding of bacterial gene expression.
Rho Independent Mechanism
Rho independent mechanism, also called intrinsic termination, relies on DNA sequences forming a GC-rich hairpin in the nascent RNA, followed by a U-rich tract. This structure pauses RNA polymerase and releases the transcript without proteins.
Rho Dependent Mechanism
Rho dependent mechanism involves the Rho protein binding to C-rich rut sites on mRNA, using ATP helicase activity to translocate and disrupt the transcription complex at specific stop points.
Why Not Ubiquitin Pathway
Ubiquitin pathway is unrelated to transcription; it’s a eukaryotic process tagging proteins for proteasome degradation via ubiquitin ligation, not involved in prokaryotic RNA polymerase release.
Why Not Dicer
Dicer is an eukaryotic RNase III enzyme that cleaves double-stranded RNA into siRNAs or miRNAs for gene silencing, absent in prokaryotes which lack RNAi pathways.
