Transcription and Translation · USMLE Step 1

During translation termination, what causes the release of the completed polypeptide from the ribosome?

  1. Encounter of a stop codon and binding of release factors
  2. Depletion of charged tRNAs available in the cytoplasm
  3. Endonucleolytic degradation of the mRNA being read
  4. Hydrolysis of GTP bound to elongation factor EF-G
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Correct answer: Encounter of a stop codon and binding of release factors

When a ribosome reaches a stop codon, no corresponding tRNA exists. Instead, release factors bind and promote hydrolysis of the bond between the polypeptide and tRNA, freeing the completed protein.

Difficulty: Medium Question 16 of 22

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