Question

The Shine--Dalgarno sequence is located in:

• A. Promoter region
• B. 52 untranslated region of mRNA
• C. Coding sequence
• D. Terminator region

Hint:

Associate "Shine-Dalgarno" with "Prokaryotic Ribosome Binding" and remember it must be on the mRNA \textit{before} the start codon, hence the 5' UTR. The eukaryotic equivalent is the Kozak consensus sequence.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The Shine-Dalgarno (SD) sequence is a specific ribosomal binding site found in bacterial and archaeal messenger RNA (mRNA).
It plays a crucial role in recruiting the ribosome to the mRNA to correctly initiate protein synthesis.

Step 2: Detailed Explanation:
Let's analyze the correct location for this sequence.
- The SD sequence is typically located a short distance (about 8 bases) upstream of the translation start codon (usually AUG).
- By molecular biology definition, the region of an mRNA molecule that is upstream of the start codon and is not translated into protein is called the 5' untranslated region (5' UTR).
- It functions by base-pairing with a complementary anti-Shine-Dalgarno sequence located near the 3' end of the 16S rRNA within the 30S small ribosomal subunit.
- \textit{Note regarding the options:} The text "52 untranslated region" in the image is a typographical error for "5' untranslated region".
- Other options like the Promoter (which is on DNA, not mRNA) and Coding sequence (which is downstream of the start codon) are incorrect.

Step 3: Final Answer:
The sequence is located in the 5' untranslated region of the mRNA transcript.
Therefore, option (B) is the correct answer.