Termination

Definition

Termination is the final step in the processes of DNA replication, transcription, and translation where synthesis of nucleic acids or proteins ceases. This critical event ensures that the genetic information is accurately passed on during replication, that RNA synthesis concludes at specific sites, and that protein assembly is completed properly, contributing to cellular function and regulation.

5 Must Know Facts For Your Next Test

1. In DNA replication, termination occurs when the replication fork reaches a specific sequence known as a terminator, ensuring that DNA synthesis is completed without errors.
2. During transcription, termination can involve specific sequences or factors that signal RNA polymerase to stop synthesizing RNA, often resulting in a polyadenylation signal in eukaryotes.
3. In translation, termination is marked by the recognition of stop codons (UAA, UAG, UGA) by release factors, which leads to the disassembly of the ribosome and the release of the polypeptide chain.
4. Proper termination is vital for maintaining genetic integrity and function; mistakes during this process can lead to incomplete or faulty molecules, potentially causing cellular dysfunction.
5. In bacteria, termination can occur via intrinsic mechanisms that form a hairpin structure in the RNA or through rho-dependent mechanisms involving additional proteins.

Review Questions

• How does termination in DNA replication ensure genetic integrity?
  • Termination in DNA replication occurs at specific sequences called terminators that signal when to stop synthesizing new strands. This process helps ensure that both daughter DNA molecules are complete and identical to the original template. By having defined endpoints for replication, cells minimize the risk of incomplete or erroneous DNA, thereby preserving genetic integrity as it divides.
• Discuss the differences between termination in transcription and translation.
  • Termination in transcription involves specific sequences that signal RNA polymerase to stop synthesizing RNA, often leading to polyadenylation in eukaryotes. In contrast, translation termination is signaled by stop codons recognized by release factors, which cause the disassembly of the ribosome and release of the polypeptide. While both processes ensure completion of their respective syntheses, they utilize different signals and mechanisms reflective of their distinct functions in gene expression.
• Evaluate how errors in the termination process can impact cellular function and overall gene expression.
  • Errors in termination can lead to incomplete or improperly synthesized molecules, which can severely affect cellular function. For instance, if transcription does not terminate correctly, it may produce excessively long or non-functional RNA transcripts that interfere with normal protein synthesis. Similarly, mistakes during translation termination can result in truncated or misfolded proteins that could disrupt cellular processes and contribute to diseases. Therefore, accurate termination is crucial for maintaining homeostasis within cells and proper gene expression.

Related terms

Replication Fork: The area where the DNA double helix is unwound, allowing for the synthesis of new DNA strands during replication.

Promoter:

A specific DNA sequence where RNA polymerase binds to initiate transcription before elongation and termination occur.

Release Factor: A protein that recognizes the stop codon during translation termination, facilitating the release of the newly synthesized polypeptide chain.