Answer: It is important that a signal to stop translation be part of protein synthesis because if there is no stop codon to signal the end of translation, amino acids will continuously be added to the polypeptide chain and this will lead to a mutated and nonfunctional protein.
Explanation: Translation starts when the ribosome encounters a codon on the mRNA AUG that signals the beginning of the polypeptide. The mRNA codon that signals the beginning of the polypeptide is called the start codon. Likewise, translation stops when the ribosome encounters a stop or termination codon. A stop or termination codon signals the termination of translation. There are three termination codons: UAA, UAG and UGA. Without a termination codon that signals end of translation, protein synthesis will continue leading to the production of a nonfunctional protein.