Termination

Definition

Termination is the final step in the processes of transcription and translation, where RNA synthesis or protein synthesis is concluded. During transcription, this involves recognizing specific sequences in the DNA that signal the end of RNA synthesis, while in translation, it is marked by reaching a stop codon that signals the release of the newly formed polypeptide chain. This critical process ensures that genetic information is accurately conveyed from DNA to RNA and then translated into functional proteins.

5 Must Know Facts For Your Next Test

1. In transcription, termination occurs when RNA polymerase encounters a termination signal in the DNA sequence, leading to the release of the synthesized RNA molecule.
2. There are different mechanisms of termination in transcription, including intrinsic (or Rho-independent) termination and Rho-dependent termination.
3. In translation, termination requires specific proteins called release factors that recognize stop codons and facilitate the disassembly of the ribosome and release of the polypeptide.
4. The proper functioning of termination is essential for gene expression regulation and ensures that proteins are synthesized correctly to perform their biological functions.
5. Errors during termination can lead to incomplete proteins or mRNA that may not function properly, potentially resulting in cellular malfunction or disease.

Review Questions

• Explain how termination differs between transcription and translation and why these differences are important.
  • Termination in transcription involves recognizing specific sequences on the DNA template that signal the end of RNA synthesis, which can occur through various mechanisms. In contrast, translation termination happens when a ribosome encounters a stop codon on mRNA, leading to the release of the newly formed polypeptide with the help of release factors. Understanding these differences is crucial because they highlight how genetic information flows from DNA to functional proteins while ensuring accuracy and efficiency in both processes.
• Discuss the role of release factors in translation termination and how they contribute to protein synthesis.
  • Release factors are essential proteins that bind to the ribosome when a stop codon is reached during translation. Their primary role is to promote hydrolysis of the bond between the polypeptide chain and the tRNA in the P-site, leading to the release of the completed protein. This process ensures that protein synthesis is concluded properly, allowing for correct folding and functioning of the newly synthesized protein, which is vital for cellular operations.
• Evaluate how errors in termination processes can affect cellular function and what implications this may have for organisms.
  • Errors during termination can lead to truncated proteins or faulty mRNA molecules, impacting cellular function significantly. Incomplete proteins may lack essential functional domains required for their biological activities, leading to malfunctions in critical pathways such as metabolism or signaling. For organisms, such disruptions can result in diseases or developmental issues, underscoring the importance of precise termination mechanisms in maintaining cellular health and proper organismal development.

Related terms

Stop Codon: A nucleotide triplet within mRNA that signals the termination of protein synthesis, indicating that the ribosome should release the completed polypeptide chain.

Promoter: A specific DNA sequence that signals the start of transcription, providing a binding site for RNA polymerase and determining where transcription begins.

RNA Polymerase: An enzyme responsible for synthesizing RNA from a DNA template during transcription, playing a key role in elongation and ultimately in termination.