During translation, amino acid chain elongation occurs until __________.

• A. no further amino acids are needed by the cell
• B. all tRNAs are empty
• C. the polypeptide is long enough
• D. the ribosome encounters a "stop" codon

Answer: (D)

Verified step by step guidance

1. Understand the process of translation: Translation is the process by which ribosomes synthesize proteins using mRNA as a template. It involves initiation, elongation, and termination phases.
2. Identify the role of codons: Codons are sequences of three nucleotides on the mRNA that correspond to specific amino acids or signal termination. During elongation, tRNA molecules bring amino acids to the ribosome, matching their anticodons with the mRNA codons.
3. Recognize the significance of a 'stop' codon: A 'stop' codon is a specific sequence on the mRNA (such as UAA, UAG, or UGA) that signals the termination of protein synthesis. It does not code for an amino acid but instead instructs the ribosome to release the completed polypeptide chain.
4. Understand the termination process: When the ribosome encounters a 'stop' codon during translation, release factors bind to the ribosome, prompting it to release the newly synthesized polypeptide chain and disassemble the translation machinery.
5. Conclude the elongation phase: The elongation of the amino acid chain continues until the ribosome reaches a 'stop' codon, at which point the translation process is terminated, and the complete protein is released.