UAG

Definition

UAG is one of the three stop codons in the genetic code, signaling the termination of protein synthesis during translation. It plays a critical role in ensuring that proteins are produced correctly, as it marks the end of an amino acid sequence. Understanding UAG is essential for grasping how genetic information is converted into functional proteins.

5 Must Know Facts For Your Next Test

1. UAG is one of three stop codons, along with UAA and UGA, which signal the end of protein synthesis.
2. When a ribosome encounters UAG during translation, it releases the newly synthesized polypeptide chain from the tRNA.
3. Stop codons do not correspond to any amino acids; instead, they trigger the release factors that lead to termination.
4. The presence of UAG in an mRNA sequence is crucial for preventing the production of nonfunctional or truncated proteins.
5. Mutations that create or eliminate stop codons like UAG can have significant impacts on gene expression and protein function.

Review Questions

• How does UAG function in the context of protein synthesis and what would happen if it were missing from an mRNA sequence?
  • UAG functions as a stop codon during protein synthesis, signaling the ribosome to terminate translation. If UAG were missing from an mRNA sequence, translation could continue beyond the intended stop point, potentially resulting in elongated polypeptides that may not fold correctly or function properly. This could lead to dysfunctional proteins that can disrupt cellular processes.
• Discuss the significance of stop codons like UAG in maintaining the integrity of protein synthesis and overall cellular function.
  • Stop codons like UAG are vital for maintaining the integrity of protein synthesis because they ensure that proteins are synthesized according to their genetic blueprint. By providing clear signals for termination, these codons prevent errors during translation, which can lead to nonfunctional or harmful proteins. This quality control mechanism is crucial for cellular health, as misfolded or aberrant proteins can lead to diseases and affect metabolic pathways.
• Evaluate the implications of mutations that affect stop codons such as UAG on gene expression and potential disease states.
  • Mutations that alter stop codons like UAG can have profound implications for gene expression and lead to various disease states. For instance, a mutation that converts UAG into a sense codon could result in the production of an abnormally long protein, which may disrupt normal cellular functions and contribute to conditions such as cancer. Conversely, mutations that create premature stop codons could lead to truncated proteins that lack essential functional domains, potentially causing genetic disorders or other health issues. Understanding these implications highlights the importance of precise coding in DNA and its effects on organismal biology.

Related terms

Codon: A sequence of three nucleotides in mRNA that corresponds to a specific amino acid or a stop signal during protein synthesis.

Translation: The process by which ribosomes synthesize proteins using mRNA as a template, translating the genetic code into a polypeptide chain.

Ribosome: A molecular machine made of ribosomal RNA and proteins that facilitates the translation of mRNA into proteins.