What occurs during the initiation phase of translation?

During the initiation phase of translation, the ribosome assembles around the target mRNA and the first tRNA is loaded. This process begins when the small ribosomal subunit binds to the mRNA molecule, identifying the start codon, typically AUG. The first tRNA molecule, carrying the corresponding amino acid (methionine for AUG), binds to this codon through complementary base pairing.

This step is critical as it sets the stage for the ribosome to begin synthesizing a protein. The availability and proper positioning of the tRNA ensure that the amino acids are added in the correct sequence as dictated by the mRNA. The large ribosomal subunit then joins this complex, completing the assembly of the functional ribosome that will carry out the elongation phase of translation by adding amino acids in a growing polypeptide chain.

In contrast, disassembly of the ribosomal subunits, degradation of mRNA, or linking amino acids are not actions taking place during the initiation phase. Disassembly refers to the end of translation, whereas degradation and linking amino acids pertain to processes that occur after initiation has been successfully completed.