Question

During translation, chain elongation continues until what happens?

a.No further amino acids are needed by the cell
b.All tRNAs are empty
c.The polypeptide is long enough
d.A stop codon is encountered
e.The ribosomes run off the end of mRNA

Answer 1

Chain elongation during translation continues until a stop codon (UAA, UAG, or UGA) is encountered, triggering the release of the polypeptide chain and the dissociation of the ribosome.

Step-by-step explanation:

During translation, chain elongation continues as tRNAs bring amino acids to the ribosome and a polypeptide chain is formed. This chain elongation proceeds until a stop codon (UAA, UAG, or UGA) is encountered on the mRNA strand. These stop codons are recognized by release factors that cause the ribosome to halt translation, release the polypeptide, and disassemble. The stop codon does not code for an amino acid and there is no corresponding tRNA that matches these codons.

Specifically, during the elongation stage of translation, charged tRNA binds to the mRNA at the A site of the ribosome, a peptide bond forms between the adjacent amino acids, and the ribosome shifts along the mRNA by one codon. Once the ribosome reaches one of the stop codons during the termination stage, the newly made protein is released and the ribosome subunits dissociate from the mRNA, completing the process of protein synthesis.