How would the deletion of the Shine–Dalgarno sequence affect a bacterial mRNA?

• A. It would increase the stability of the mRNA, resulting in higher protein production.
• B. It would cause premature termination of transcription.
• C. It would prevent ribosome binding, leading to reduced or absent translation of the mRNA.
• D. It would enhance the accuracy of translation by improving codon recognition.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the role of the Shine–Dalgarno sequence in bacterial mRNA. It is a ribosomal binding site located upstream of the start codon that helps the ribosome recognize and bind to the mRNA for translation initiation.
2. Step 2: Consider what happens if the Shine–Dalgarno sequence is deleted. Without this sequence, the ribosome cannot properly align with the start codon on the mRNA.
3. Step 3: Analyze the consequence of impaired ribosome binding. If the ribosome cannot bind, translation initiation is severely reduced or completely blocked, leading to little or no protein synthesis from that mRNA.
4. Step 4: Differentiate this effect from other processes. The Shine–Dalgarno sequence does not affect mRNA stability or transcription termination, so those options are less likely.
5. Step 5: Conclude that deletion of the Shine–Dalgarno sequence prevents ribosome binding, which results in reduced or absent translation of the mRNA.