During which step of translation are amino acids specifically added to the growing polypeptide chain?

During the process of translation, the elongation phase is where amino acids are specifically added to the growing polypeptide chain. This stage occurs after the initiation phase, where the ribosome assembles around the mRNA and the first tRNA (transfer RNA) molecule is attached, bringing the first amino acid.

During elongation, subsequent tRNA molecules, each carrying a specific amino acid corresponding to the next codon on the mRNA, bind to the ribosome. The ribosome facilitates the formation of peptide bonds between the amino acids, effectively lengthening the polypeptide chain. This process continues as the ribosome moves along the mRNA strand, reading the codons and adding the appropriate amino acids until the entire protein is synthesized.

Processing does not take place during translation itself; instead, it refers to post-translational modifications that proteins undergo after they have been synthesized. Initiation is the step where translation begins, and termination is the step that concludes the translation process when a stop codon is reached, thereby releasing the completed polypeptide chain. Hence, the addition of amino acids specifically occurs during elongation, making this the correct answer.