Termination

Definition

Termination is the final step in the processes of transcription and translation, where the synthesis of RNA or protein is concluded. This crucial event ensures that the molecular machinery knows when to stop adding nucleotides during transcription or amino acids during translation, allowing for the proper completion of genes and the correct folding of proteins.

5 Must Know Facts For Your Next Test

1. In prokaryotes, termination occurs through the recognition of specific sequences in the RNA that signal RNA polymerase to detach from the DNA template.
2. Eukaryotic termination involves complex interactions with additional proteins and modifications to the pre-mRNA before it becomes mature mRNA.
3. During translation termination, a release factor binds to the ribosome when it encounters a stop codon, leading to the release of the newly synthesized protein.
4. Termination ensures that only complete and correctly processed transcripts are produced, which is essential for maintaining cellular function and preventing errors in protein synthesis.
5. Failure in the termination process can lead to incomplete proteins, which can disrupt cellular processes and contribute to diseases.

Review Questions

• How does termination differ between prokaryotic and eukaryotic organisms in transcription?
  • In prokaryotic organisms, termination occurs through a simpler mechanism where specific sequences in the RNA signal RNA polymerase to stop transcription and dissociate from the DNA. In contrast, eukaryotic termination is more complex, involving additional proteins that interact with RNA polymerase and require post-transcriptional modifications like polyadenylation to process pre-mRNA into mature mRNA before it is fully released.
• What role do stop codons play in the termination of translation, and how do release factors contribute to this process?
  • Stop codons are essential components of mRNA that signal the end of translation by instructing ribosomes to cease protein synthesis. When a ribosome encounters a stop codon, a release factor binds to it, prompting the ribosome to release the newly synthesized polypeptide chain. This process ensures that proteins are completed correctly and can fold into their functional shapes.
• Evaluate how improper termination can affect cellular processes and lead to disease states.
  • Improper termination can lead to incomplete or dysfunctional proteins being synthesized, disrupting normal cellular processes such as metabolism, signaling, and structural integrity. For instance, if a protein doesn't terminate correctly due to a mutation in the coding sequence or issues with associated factors, it may result in malfunctioning enzymes or structural proteins. Such anomalies can contribute to various diseases, including cancer and genetic disorders, highlighting the importance of accurate termination in gene expression.

Related terms

Stop Codon: A specific nucleotide triplet within mRNA that signals the termination of translation, resulting in the release of the completed polypeptide chain.

Ribosome: The cellular structure composed of ribosomal RNA and proteins, responsible for synthesizing proteins by translating messenger RNA into a polypeptide chain.

Promoter:

A DNA sequence that initiates transcription of a particular gene, providing a binding site for RNA polymerase and other necessary transcription factors.