Question

The consensus sequence 5'-ACCAUGG-3'; is also known as

• A. Kozak sequence
• B. Shine-Dalgarno sequence
• C. Transcription termination signal sequence
• D. D-loop of tRNA

Hint:

To remember translation initiation sequences:
- Prokaryotes: Shine-Dalgarno sequence ($5'-\text{AGGAGG}-3'$).
- Eukaryotes: Kozak sequence ($5'-\text{ACCAUGG}-3'$).

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Translation initiation in living organisms requires the ribosome to identify the correct start codon (AUG) on the messenger RNA (mRNA) transcript.
This selection is guided by specific consensus sequences flanking the start codon.

Step 2: Detailed Explanation:
Let us analyze the consensus sequences associated with translation:
- Kozak Sequence: In eukaryotic organisms, translation initiation is facilitated by a consensus sequence surrounding the initiator codon.
This sequence, identified by Marilyn Kozak, is standardly represented as:
\[ 5'-\text{gccRccAUGG}-3' \]
where R is a purine (adenine or guanine).
The core consensus sequence is frequently conserved as $5'-\text{ACCAUGG}-3'$.
The ribosome recognizes this sequence during the scanning process, which ensures the correct start codon is chosen for translation.
- Let us review the incorrect options:
- Shine-Dalgarno Sequence: This is the ribosomal binding site in prokaryotes, located 8 base pairs upstream of the start codon, with a consensus sequence of $5'-\text{AGGAGG}-3'$.
- Transcription termination signal: These are DNA sequences (like polyadenylation signals in eukaryotes or hairpins in prokaryotes) that signal the end of transcription, not translation.
- D-loop of tRNA: A structural arm of tRNA containing dihydrouridine, unrelated to mRNA translation initiation.
Therefore, the consensus sequence $5'-\text{ACCAUGG}-3'$ is the Kozak sequence.

Step 3: Final Answer:
The consensus sequence $5'-\text{ACCAUGG}-3'$ is known as the Kozak sequence.