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Multiple Choice
Which of the following best describes the initiation of translation?
A
The completed polypeptide is released from the ribosome after a stop codon is reached.
B
The small ribosomal subunit binds to the mRNA and the initiator tRNA, followed by the joining of the large ribosomal subunit.
C
The ribosome moves along the mRNA, adding amino acids to the polypeptide chain.
D
A peptide bond is formed between two amino acids on the growing polypeptide chain.
Verified step by step guidance
1
Step 1: Understand the process of translation initiation. Translation is the process by which ribosomes synthesize proteins using mRNA as a template. The initiation phase is the first step in translation and involves the assembly of the ribosome and the recruitment of the initiator tRNA.
Step 2: Identify the role of the small ribosomal subunit. During initiation, the small ribosomal subunit binds to the mRNA at the start codon (usually AUG). This ensures that translation begins at the correct location on the mRNA.
Step 3: Recognize the role of the initiator tRNA. The initiator tRNA carries the amino acid methionine (Met) and pairs with the start codon on the mRNA. This pairing is facilitated by complementary base pairing between the anticodon of the tRNA and the codon on the mRNA.
Step 4: Understand the joining of the large ribosomal subunit. After the small ribosomal subunit and initiator tRNA are bound to the mRNA, the large ribosomal subunit joins to form a complete ribosome. This marks the end of the initiation phase and prepares the ribosome for elongation.
Step 5: Compare the options provided in the problem. The correct description of translation initiation is: 'The small ribosomal subunit binds to the mRNA and the initiator tRNA, followed by the joining of the large ribosomal subunit.' This matches the biological process described above.