Question

In case of prokaryotes, the start codon is usually preceded by a sequence complementary to the

• A. 16S rRNA
• B. 5S rRNA
• C. 28S rRNA
• D. 18S rRNA

Hint:

In prokaryotic translation, always remember that the Shine-Dalgarno sequence on mRNA pairs with the 16S rRNA to initiate protein synthesis.

Answer 1

The Correct Option is A

Step 1: Translation initiation in prokaryotes 
In prokaryotes, translation begins when the ribosome assembles at the start codon (AUG) on the mRNA. However, efficient recognition of the start codon requires a special upstream sequence known as the Shine-Dalgarno sequence. 
Step 2: Role of the Shine-Dalgarno sequence 
The Shine-Dalgarno sequence is a purine-rich region located about 6--10 nucleotides upstream of the start codon on mRNA. It base-pairs with a complementary sequence on the 3$^\prime$ end of the 16S rRNA of the small (30S) ribosomal subunit. 
Step 3: Function of 16S rRNA in initiation 
This base-pairing helps align the ribosome correctly with the start codon and is essential for the initiation of protein synthesis in prokaryotes. Therefore, the correct answer is: 16S rRNA.