Termination

Definition

Termination is the final step in the process of gene expression where the synthesis of RNA or protein ceases. This crucial process involves specific signals that signal the end of transcription or translation, leading to the release of newly synthesized molecules and the disassembly of the molecular machinery involved. Understanding how termination works is vital as it ensures proper gene expression and prevents errors in protein synthesis.

5 Must Know Facts For Your Next Test

1. In prokaryotes, termination often involves specific sequences in the DNA called terminators that signal RNA polymerase to stop transcription.
2. In eukaryotes, termination of transcription can involve complex factors such as polyadenylation signals that lead to cleavage and release of the RNA molecule.
3. During translation, termination occurs when a stop codon is encountered on the mRNA, which triggers the release factors to disassemble the ribosome and release the polypeptide chain.
4. The accuracy of termination is critical; improper termination can lead to truncated proteins or errors in gene expression that can disrupt cellular functions.
5. Termination mechanisms can vary significantly between prokaryotic and eukaryotic organisms, highlighting the evolutionary adaptations in their respective genetic processes.

Review Questions

• How does the mechanism of termination differ between prokaryotic and eukaryotic transcription?
  • In prokaryotic transcription, termination typically relies on specific sequences known as terminators that cause RNA polymerase to detach from the DNA. In contrast, eukaryotic transcription involves more complex mechanisms including signal sequences that prompt RNA processing events like polyadenylation, which ultimately leads to cleavage and release of the RNA transcript. This difference highlights the evolutionary complexity in eukaryotic cells, requiring additional steps for accurate gene expression.
• Discuss the role of stop codons in translation termination and their significance in protein synthesis.
  • Stop codons are crucial during translation termination as they signal the end of the polypeptide chain synthesis. When a ribosome encounters a stop codon on the mRNA, it recruits release factors that facilitate disassembly of the ribosome and release of the newly formed protein. This process ensures that proteins are synthesized correctly and completely, which is essential for proper cellular function. Errors in recognizing stop codons can lead to incomplete proteins, affecting cellular processes.
• Evaluate how disruptions in termination processes can impact gene expression and cellular function.
  • Disruptions in termination processes can lead to significant consequences for gene expression and overall cellular function. If transcription or translation does not terminate properly, it can result in incomplete RNA or proteins that may not fold correctly or function as intended. Such anomalies can disrupt metabolic pathways, lead to disease states, or result in malfunctioning proteins that may cause cellular stress or apoptosis. Therefore, understanding and maintaining proper termination mechanisms is vital for organismal health and viability.

Related terms

RNA Polymerase: An enzyme that synthesizes RNA from a DNA template during transcription, playing a key role in both prokaryotic and eukaryotic systems.

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

Promoter:

A specific DNA sequence where RNA polymerase binds to initiate transcription, playing a role in determining where transcription begins and ultimately influencing termination.