41. Prokaryotic ribosomes bind to which one of the following:
(a) Kozak sequence,
(b) Ori sequence,
(c) Promoter sequence,
(d) Shine-Dalgarno sequence,

What Sequence Do Prokaryotic Ribosomes Bind To?

Protein synthesis is a tightly regulated process that begins with the initiation of translation. In prokaryotic organisms, such as bacteria, this process relies heavily on the ribosome recognizing a specific mRNA sequence to begin translation at the correct start codon.

Let’s evaluate the options given:

(a) Kozak sequence

The Kozak sequence is found in eukaryotic mRNA and plays a critical role in initiating translation in eukaryotic cells—not prokaryotes.

(b) Ori sequence

Ori stands for origin of replication, which is a DNA sequence involved in the initiation of DNA replication, not translation.

(c) Promoter sequence

A promoter sequence is involved in transcription, not translation. It’s where RNA polymerase binds to initiate the synthesis of mRNA.

(d) Shine-Dalgarno sequence

Correct Answer: The Shine-Dalgarno sequence is a prokaryotic mRNA sequence located just upstream of the start codon (AUG). It is recognized by the 16S rRNA component of the 30S ribosomal subunit. This binding ensures that the ribosome correctly positions itself on the mRNA to begin translation at the right site.

Why the Shine-Dalgarno Sequence Is Important

• Ensures precise translation start: Aligns the ribosome with the start codon.

• Ribosome recruitment: Facilitates the binding of the 30S ribosomal subunit to mRNA.

• Unique to prokaryotes: Eukaryotic mRNAs lack this sequence and use a different mechanism (Kozak sequence) for initiation.

Final Answer:

(d) Shine-Dalgarno sequence

In prokaryotic translation, ribosomes bind to the Shine-Dalgarno sequence to initiate protein synthesis at the correct start site.