Termination

Definition

Termination refers to the final stage of a biological process, where the synthesis of a nucleic acid or protein is completed. In DNA replication, it involves the end of the replication process when DNA polymerase detaches from the DNA strand, while in transcription and translation, it signifies the completion of RNA synthesis or polypeptide formation, leading to the release of the newly synthesized molecule.

5 Must Know Facts For Your Next Test

1. In DNA replication, termination is typically characterized by the completion of new DNA strands, which are checked for errors before cell division.
2. During transcription, termination often involves specific sequences in the DNA template that signal RNA polymerase to stop synthesizing RNA.
3. In translation, the presence of a stop codon on the mRNA prompts the ribosome to release the completed polypeptide chain and disassemble.
4. Termination processes are essential for ensuring that genetic information is accurately passed on and expressed in proteins.
5. Factors such as proteins and specific sequences play a significant role in recognizing termination signals and ensuring efficient completion of these processes.

Review Questions

• How does termination differ in DNA replication compared to transcription?
  • In DNA replication, termination occurs when DNA polymerase reaches the end of the template strand and detaches after synthesizing a complete double-stranded DNA molecule. This involves specific sequences or structures like telomeres that signal the end of replication. In contrast, transcription termination happens when RNA polymerase encounters specific sequences in the DNA that indicate it should stop synthesizing RNA. This difference is crucial because one process creates a stable DNA structure, while the other produces a transient RNA molecule that will be translated into protein.
• What roles do stop codons play in the termination of translation?
  • Stop codons are essential signals in mRNA that mark the end of translation. When a ribosome encounters one of these codons during protein synthesis, it triggers the recruitment of release factors instead of tRNA. These release factors facilitate the disassembly of the ribosomal complex and promote the release of the newly synthesized polypeptide chain. This process ensures that proteins are produced accurately and only when they are fully assembled, maintaining cellular function.
• Evaluate how mutations in termination signals could impact gene expression and protein synthesis.
  • Mutations in termination signals can have significant consequences for gene expression and protein synthesis. For instance, if a mutation alters a stop codon into a sense codon, this could lead to read-through translation where ribosomes continue adding amino acids beyond what was intended. Such aberrations can result in longer polypeptides that may be dysfunctional or have altered properties, potentially leading to diseases or malfunctions within cells. Thus, accurate termination is critical for producing functional proteins and maintaining cellular homeostasis.

Related terms

DNA polymerase: An enzyme responsible for synthesizing new strands of DNA by adding nucleotides complementary to the template strand during DNA replication.

RNA polymerase: An enzyme that catalyzes the synthesis of RNA from a DNA template during transcription, playing a crucial role in gene expression.

Stop codon: A specific nucleotide triplet within mRNA that signals the termination of translation, instructing the ribosome to stop protein synthesis.