Question: 110: The process of translation of mRNA to proteins begins as soon as :
(1) Both the subunits join together to bind with mRNA
(2) The tRNA is activated and the larger subunit of ribosome encounters mRNA
(3) The small subunit of ribosome encounters mRNA
(4) The larger subunit of ribosome encounters mRNA
Answer: Option (3)
Explanation:
Translation is the process by which the nucleotide sequence of mRNA is decoded to synthesize a polypeptide.
The initiation of translation begins when the small subunit of the ribosome binds to the mRNA molecule.
In prokaryotes, the small ribosomal subunit recognizes and binds to the Shine–Dalgarno sequence on mRNA, while in eukaryotes it binds near the 5′ cap and scans for the start codon.
After the small subunit binds to mRNA, the initiator tRNA carrying methionine pairs with the start codon.
Only after this complex is formed does the large ribosomal subunit join to complete the initiation complex.
Therefore, translation begins as soon as the small subunit of the ribosome encounters mRNA,
making Option (3) correct.