[Campbell Biology P.401] Which of the following is an accurate description of the terminatio... | Practice Question

Which of the following is an accurate description of the termination of translation?

  • A: Stop codons (UAG, UAA, UGA) code for specific amino acids that signal the end of translation.
  • B: A release factor, which is a protein shaped like an aminoacyl tRNA, binds directly to the stop codon in the A site.
  • C: Termination involves the addition of a hydroxyl group to the polypeptide chain, releasing it from the tRNA in the P site.
  • D: Breakdown of the translation assembly requires the hydrolysis of only one GTP molecule.

Explanation

Termination of translation occurs when a stop codon UAG, UAA, or UGA enters the A site. These codons do not code for amino acids. Instead, a release factor, a protein resembling an aminoacyl tRNA, binds to the stop codon. This binding leads to the addition of a water molecule to the polypeptide chain, hydrolyzing the bond between the polypeptide and the tRNA in the P site, thereby releasing the completed polypeptide. The subsequent breakdown of the translation assembly requires the hydrolysis of two additional GTP molecules.