Which subunit encounters an mRNA ,to begin the process of translation of the mRNA to protein ?

Small subunit of ribosome.

The correct answer is Option (2)-Small subunit of ribosome.

In the process of translation, the small subunit of the ribosome is the one that encounters the mRNA to initiate the translation of mRNA into protein.

The cellular factory responsible for synthesising proteins is the ribosome. The ribosome consists of structural RNAs and about 80 different proteins. In its inactive state, it exists as two subunits; a large subunit and a small subunit. When the small subunit encounters an mRNA, the process of translation of the mRNA to protein begins. There are two sites in the large subunit, for subsequent amino acids to bind to and thus, be close enough to each other for the formation of a peptide bond. The ribosome also acts as a catalyst (23S rRNA in bacteria is the enzyme- ribozyme) for the formation of peptide bond.