Final answer:
The statement is true; a codon signifies either a specific amino acid or a stop signal in protein synthesis. Stop codons mark the end of protein synthesis, and the genetic code is both unambiguous and redundant, with AUG acting as the start codon.
Step-by-step explanation:
A codon does indeed signify either a specific amino acid or a stop signal during the process of protein synthesis. This statement is true. In the genetic code, most codons correspond to one of the 20 amino acids used to build proteins. However, three of the 64 possible codon combinations, specifically UGA, UAA, and UAG, are known as stop codons or nonsense codons. These stop codons do not encode any amino acids and serve to terminate the protein synthesis process, releasing the newly formed polypeptide chain from the translation machinery.