Final Answer:
The assembly of the translation complex:
b. Initiator tRNA
Step-by-step explanation:
During the assembly of the translation complex, the initiator tRNA is the component that binds first to mRNA. This process marks the initiation of translation, a crucial step in protein synthesis. The initiator tRNA carries the amino acid methionine and recognizes the start codon on the mRNA sequence.
The interaction between the initiator tRNA and the mRNA is facilitated by initiation factors, forming a stable complex. This binding of the initiator tRNA to the mRNA is a key event that prepares the mRNA and ribosomal subunits for the subsequent steps in translation.
The small ribosomal subunit also plays a vital role in translation, but it comes into play after the initiator tRNA-mRNA interaction. The small ribosomal subunit binds to the mRNA along with other initiation factors, creating a platform for the initiator tRNA to locate the start codon.
Once the initiation complex is established, the large ribosomal subunit joins, completing the formation of the functional ribosome for the elongation phase of translation. Therefore, while both ribosomal subunits are essential, the initiator tRNA takes the lead by binding first to the mRNA during the initiation of translation.