During which process does tRNA move to the P site, the empty tRNA exits from the E site, and the A site codon is ready for the next tRNA?

• A. Transcription
• B. Translocation
• C. Translation
• D. Replication

Answer: (B)

Translocation is the step in translation where the ribosome moves along the mRNA and tRNAs shift between sites. After the new amino acid is added to the growing peptide, the tRNA in the P site moves to the E site and exits, while the tRNA in the A site moves to the P site. This movement clears the A site so the next aminoacyl-tRNA can enter and pair with the next codon. Translation is the overall process of making protein, but the specific movement of tRNAs between A, P, and E sites described here is translocation. Transcription and replication involve RNA synthesis and DNA duplication, respectively, and do not describe this tRNA site-shifting step.