Termination

Definition

Termination refers to the process of ending transcription and translation, where the synthesis of RNA and polypeptides is completed, respectively. In both processes, specific signals dictate when to stop adding nucleotides or amino acids, leading to the final product of either mRNA or a functional protein. This process is crucial for gene expression regulation and ensures that only the necessary proteins are produced at the right time.

5 Must Know Facts For Your Next Test

1. In transcription, termination occurs when RNA polymerase encounters a terminator sequence in the DNA, leading to the release of newly synthesized RNA.
2. During translation, termination is triggered by the recognition of a stop codon by a release factor, which prompts the ribosome to disassemble.
3. Proper termination ensures that mRNA transcripts are complete and ready for translation, avoiding premature stop signals that can lead to dysfunctional proteins.
4. In eukaryotes, termination of transcription involves additional steps like cleavage and polyadenylation, which help process the mRNA for export and stability.
5. The accuracy of termination is vital; errors can result in truncated proteins that may disrupt cellular functions or lead to disease.

Review Questions

• How does termination in transcription differ from termination in translation?
  • Termination in transcription occurs when RNA polymerase reaches a specific DNA sequence known as a terminator, causing it to detach and release the completed RNA strand. In contrast, termination in translation is initiated when a stop codon on the mRNA is recognized by a release factor, signaling the ribosome to release the finished polypeptide chain. While both processes ensure that synthesis is appropriately concluded, they operate through distinct mechanisms and signals within the cell.
• What role does polyadenylation play during transcription termination in eukaryotic cells?
  • Polyadenylation plays a critical role during transcription termination in eukaryotic cells by adding a poly(A) tail to the 3' end of the newly synthesized mRNA. This modification enhances the stability of the mRNA molecule, protects it from degradation, and facilitates its export from the nucleus to the cytoplasm for translation. Polyadenylation thus contributes not only to the termination process but also to the overall regulation and efficiency of gene expression.
• Evaluate the consequences of improper termination in protein synthesis and its potential impact on cellular function.
  • Improper termination during protein synthesis can lead to incomplete or dysfunctional proteins, which may have significant consequences for cellular function. For instance, truncated proteins might lose essential functional domains required for their activity, resulting in impaired biological processes or cellular dysfunction. This can contribute to various diseases, including genetic disorders and cancer, as cells fail to produce the correct proteins needed for proper growth, development, and homeostasis. Understanding these consequences highlights the importance of precise mechanisms governing termination in both transcription and translation.

Related terms

Polyadenylation: The addition of a poly(A) tail to the 3' end of an mRNA molecule during termination, which stabilizes the mRNA and aids in its export from the nucleus.

Stop Codon: A specific sequence of three nucleotides in mRNA that signals the termination of translation, indicating that the polypeptide chain is complete.

Ribosome: The cellular machinery responsible for synthesizing proteins by translating mRNA into a polypeptide chain during the process of translation.