Attenuation

Definition

Attenuation is a regulatory mechanism in gene expression that relies on the premature termination of transcription. It is commonly seen in prokaryotes, particularly in the regulation of amino acid biosynthetic operons.

5 Must Know Facts For Your Next Test

1. Attenuation involves the formation of alternative secondary structures in the mRNA leader sequence, which can terminate or allow transcription to continue.
2. The trp operon in E. coli is a well-studied example of attenuation, where high levels of tryptophan lead to the formation of a terminator structure that halts transcription.
3. Attenuation requires closely linked processes of transcription and translation, making it predominantly observed in prokaryotes.
4. Ribosome stalling at specific codons within the leader peptide can influence whether attenuation occurs or not.
5. The presence or absence of specific charged tRNAs plays a crucial role in determining the attenuation outcome.

Review Questions

• How does attenuation regulate gene expression at the transcriptional level?
• Why is attenuation primarily observed in prokaryotes?
• What role do ribosomes play in the process of attenuation?

Related terms

Operon:

A cluster of genes under a single promoter, transcribed together producing polycistronic mRNA.

Leader Sequence: A region upstream of the coding sequence that can form secondary structures influencing transcription termination.

Riboswitch: A regulatory segment of mRNA that binds a small molecule, resulting in changes to gene expression.