UAG

Definition

UAG is a codon in the genetic code that signals the termination of protein synthesis. It is one of the three stop codons, along with UGA and UAA, that indicate the end of the coding sequence and the completion of the polypeptide chain.

5 Must Know Facts For Your Next Test

1. UAG is one of the three stop codons, along with UGA and UAA, that signal the end of protein synthesis.
2. The recognition of a stop codon by the ribosome triggers the release of the completed polypeptide chain and the dissociation of the ribosome from the mRNA.
3. Nonsense mutations that introduce a premature stop codon can lead to the production of truncated, non-functional proteins.
4. The presence of a stop codon in the mRNA sequence is crucial for ensuring the proper termination of protein synthesis and the release of the final polypeptide chain.
5. The efficiency of stop codon recognition by the ribosome is an important factor in maintaining the fidelity of protein synthesis.

Review Questions

• Explain the role of UAG in the process of protein synthesis.
  • UAG is one of the three stop codons that signal the termination of protein synthesis. When the ribosome encounters a UAG codon during translation, it recognizes this as a signal to release the completed polypeptide chain and dissociate from the mRNA. This ensures the proper termination of the protein synthesis process and the release of the final protein product.
• Describe the consequences of a nonsense mutation that introduces a premature UAG stop codon.
  • A nonsense mutation that introduces a premature UAG stop codon can lead to the production of a truncated, non-functional protein. This occurs because the ribosome will recognize the premature stop codon and release the partially synthesized polypeptide chain before the complete protein can be assembled. This can have significant consequences for the cell, as the truncated protein may lack essential functional domains or be unable to fold properly, leading to potential cellular dysfunction or disease.
• Analyze the importance of the efficiency of stop codon recognition by the ribosome in maintaining the fidelity of protein synthesis.
  • The efficient recognition of stop codons, including UAG, by the ribosome is crucial for maintaining the fidelity of protein synthesis. If the ribosome fails to recognize a stop codon or misidentifies a codon as a stop codon, it can lead to the production of incomplete or aberrant proteins that may have detrimental effects on cellular function. The ribosome's ability to accurately identify and respond to stop codons ensures the proper termination of protein synthesis and the release of the final, fully functional polypeptide chain. This high level of precision is essential for maintaining the integrity of the proteome and supporting the overall health and homeostasis of the cell.

Related terms

Stop Codon: A triplet of nucleotides in the genetic code that signals the end of protein translation and the release of the completed polypeptide chain from the ribosome.

Nonsense Mutation: A type of genetic mutation that introduces a premature stop codon, leading to the production of a truncated, non-functional protein.

Ribosome: The cellular organelle responsible for the synthesis of proteins, where the translation of mRNA into a polypeptide chain occurs.