Final answer:
Codons UAA, UGA, and UAG are stop codons in translation that signal the end of protein synthesis by terminating the addition of amino acids to the polypeptide chain. They do not code for any amino acids. In contrast, the AUG codon is a start codon, signaling the beginning of protein synthesis and setting the reading frame for translation.
Step-by-step explanation:
The codons UAA, UGA, and UAG in translation have a specific functional role. These codons are critical in the translation process as they signal the termination or end of a polypeptide chain synthesis. They are known as stop codons, and they do not encode for any amino acids, contrasting with the codons that specify amino acids to be added to the growing polypeptide chain.
The translation machinery comprises ribosomes, messenger RNA (mRNA), and transfer RNA (tRNA). Once the ribosome encounters any of these stop codons during translation, the addition of amino acids is halted, and the completed polypeptide chain is released. This signifies the end of the translation process for that particular mRNA transcript.
The other codon that has a unique function is AUG, which codes for the amino acid methionine and also serves as the start codon, marking the beginning of translation. This codon is essential for establishing the reading frame of the mRNA, enabling the ribosomes to interpret the mRNA sequence correctly in sets of three nucleotides (triplet code) to synthesize proteins correctly.