Final answer:
The initial step in the synthesis of a transmembrane protein during translation is the formation of an initiation complex, where a ribosome binds to the mRNA with an initiator tRNA and initiation factors, aligning with the start codon AUG. Option 1 is the correct answer.
Step-by-step explanation:
Initial Step in the Translation of a Transmembrane Protein
The first step in the synthesis of a transmembrane protein, or the initiation of translation, begins with the formation of an initiation complex. This complex forms when a small ribosomal subunit binds to the mRNA template, along with initiation factors and a special initiator tRNA known as tRNAMet in eukaryotes, or tRNAMetf in prokaryotes.
For the initiation step, the tRNA carries the amino acid methionine, which pairs with the start codon AUG on the mRNA.
During this stage, several other initiation factors are involved to ensure that the ribosome positions correctly at the start codon. This precision is crucial for the correct assembly of the protein.
Once the initiation complex has been successfully formed, the process moves into the elongation phase, where amino acids are successively added to form a growing polypeptide chain.
Therefore, the correct option for the initial step in the translation of the new protein is 1) Initiation.