Termination

Definition

Termination refers to the final step in the processes of transcription and translation, signaling the end of RNA synthesis in transcription and the completion of polypeptide synthesis in translation. It is a crucial event that ensures the accurate production of RNA and proteins, maintaining cellular functions. This process involves specific sequences and factors that recognize when to halt synthesis, ensuring that only the required genetic information is produced and that proteins are properly folded and functional.

5 Must Know Facts For Your Next Test

1. In prokaryotes, termination can occur through two mechanisms: Rho-dependent and Rho-independent, which involve different sequences and factors.
2. Eukaryotic termination involves additional complexities such as polyadenylation, where a poly(A) tail is added to the mRNA after transcription.
3. During translation, termination occurs when a stop codon is recognized by release factors, which leads to the disassembly of the ribosome and release of the newly formed protein.
4. Termination is essential for ensuring that mRNA is correctly processed before it exits the nucleus in eukaryotic cells.
5. Defects in termination processes can lead to improper gene expression and have implications for diseases such as cancer.

Review Questions

• How do prokaryotic and eukaryotic termination mechanisms differ in transcription?
  • Prokaryotic termination mechanisms primarily include Rho-dependent and Rho-independent pathways. Rho-dependent termination relies on a protein factor that helps detach RNA from DNA, while Rho-independent termination involves specific sequences in the RNA that form hairpin structures. In contrast, eukaryotic termination involves more complex processes, including the addition of a poly(A) tail after transcription and various factors that contribute to proper mRNA processing.
• Discuss the role of stop codons in protein synthesis termination and their significance.
  • Stop codons are essential for terminating protein synthesis during translation. When a ribosome encounters a stop codon on mRNA, it recruits release factors that trigger the disassembly of the ribosome and release of the newly synthesized polypeptide. This ensures that proteins are produced accurately and efficiently, allowing cells to maintain their functions and respond to their environment.
• Evaluate how errors in termination can impact gene expression and contribute to diseases.
  • Errors in termination can lead to incomplete or dysfunctional mRNA or proteins, disrupting normal cellular processes. For instance, faulty termination can result in the production of truncated proteins or retention of unprocessed mRNA within cells. Such issues can contribute to various diseases, including cancer, where misregulated gene expression plays a crucial role. Understanding these connections highlights the importance of accurate termination in maintaining cellular health and function.

Related terms

Promoter: A DNA sequence that signals the start of transcription, where RNA polymerase binds to initiate RNA synthesis.

Rho factor: A protein involved in prokaryotic termination of transcription, facilitating the release of newly synthesized RNA from the DNA template.

Stop codon: A specific sequence of nucleotides in mRNA that signals the termination of translation, leading to the release of the completed polypeptide chain.