What is the role of codons UAA, UGA, and UAG in translation? What events occur when one of these codons appears at the A site of the ribosome?

Key Concepts

Codons and Their Function

Codons are sequences of three nucleotides in mRNA that correspond to specific amino acids or signal the termination of protein synthesis. The codons UAA, UGA, and UAG are known as stop codons, which do not code for any amino acid but instead signal the ribosome to halt translation.

Translation Process

Translation is the process by which ribosomes synthesize proteins by decoding mRNA. During translation, the ribosome moves along the mRNA, and tRNA molecules bring the appropriate amino acids to the growing polypeptide chain. The A site of the ribosome is where the incoming tRNA binds, and the presence of a stop codon here triggers the termination of translation.

Termination of Translation

When a stop codon (UAA, UGA, or UAG) appears at the A site of the ribosome, it is recognized by release factors instead of tRNA. These factors promote the release of the newly synthesized polypeptide chain from the ribosome, leading to the disassembly of the translation complex and the completion of protein synthesis.