Final answer:
The correct term for the codons UAG, UAA, and UGA, which do not code for an amino acid and signal the end of protein synthesis, is nonsense codons or stop codons.
Step-by-step explanation:
The three codons you have mentioned, UAG, UAA, and UGA, are special codons in the genetic code that signal the termination of protein synthesis.
These are known as stop codons or nonsense codons. They do not code for an amino acid and do not have corresponding tRNA molecules. Instead, their presence in the mRNA sequence signals the release of the newly synthesized polypeptide chain from the translation machinery. Therefore, the correct answer to your question is d. Nonsense codons.