Correct option is A
The correct answer is (a). The Shine-Dalgarno sequence is crucial for translation initiation in prokaryotes, as it helps the ribosome recognize the start site for translation. A stem-loop structure formed upstream of this sequence could potentially inhibit translation by interfering with the ribosome’s ability to properly bind to the mRNA. However, this modification is not as effective at inhibiting translation compared to the other listed modifications.
(b) A stem-loop structure that incorporates the Shine-Dalgarno sequence would block the ribosome's access to the mRNA, thereby inhibiting translation initiation.
(c) eIF2 is involved in translation initiation in eukaryotes. A mutant mimicking its phosphorylated state would inhibit translation because phosphorylation of eIF2 prevents the formation of the translation initiation complex.
(d) A mutation that leads to a decrease in the processivity of the capping enzyme would prevent the proper capping of mRNAs. A lack of a cap structure would make the mRNA unstable and unable to be translated effectively.
Information Booster:
The Shine-Dalgarno sequence is critical for initiating translation in prokaryotes as it binds to the 16S rRNA of the small ribosomal subunit.
Stem-loop structures in mRNA can inhibit translation by physically blocking the ribosome from accessing the Shine-Dalgarno sequence or the start codon.
eIF2 is a key factor in translation initiation. Its phosphorylation leads to a decrease in translation efficiency by preventing the formation of the initiation complex.
The 5' cap structure in eukaryotic mRNAs is essential for stability, efficient translation initiation, and protection from exonucleolytic degradation.
Modifications that block the Shine-Dalgarno sequence, disrupt the eIF2 function, or prevent proper mRNA capping are all potent inhibitors of translation.
