What is the likely effect of each of the following mutations of the trpL region on attenuation control of trp operon gene transcription? Explain your reasoning. The entire polypeptide coding sequence of trpL is deleted.

Verified step by step guidance

1. Understand the role of the trpL region in the trp operon. The trpL region contains the leader peptide sequence and is involved in the attenuation mechanism, which regulates the transcription of the trp operon based on tryptophan levels.
2. Recognize that the leader peptide sequence in the trpL region is crucial for the formation of the attenuator structure. This structure can form a terminator or anti-terminator hairpin in the mRNA, influencing whether transcription continues or stops.
3. Consider the effect of deleting the entire polypeptide coding sequence of trpL. Without the leader peptide, the ribosome cannot stall at the tryptophan codons, which is necessary for the formation of the anti-terminator structure when tryptophan levels are low.
4. Predict that the deletion of the trpL coding sequence would likely disrupt the attenuation mechanism. Without the leader peptide, the ribosome cannot properly regulate the formation of the terminator or anti-terminator structures, potentially leading to unregulated transcription of the trp operon.
5. Conclude that the deletion of the trpL region would likely result in constitutive expression of the trp operon, as the attenuation control mechanism would be impaired, allowing transcription to proceed regardless of tryptophan levels.

Key Concepts

Attenuation Control

Attenuation control is a regulatory mechanism in prokaryotic gene expression, particularly in the trp operon, where the formation of specific RNA structures in the leader region (trpL) determines whether transcription continues or is terminated prematurely. This process relies on the availability of tryptophan and the ribosome's movement along the mRNA, influencing the formation of either a transcription-terminating or a transcription-allowing structure.

trp Operon

The trp operon is a cluster of genes in bacteria that encode enzymes necessary for the biosynthesis of the amino acid tryptophan. It is regulated by both repression and attenuation mechanisms, allowing the cell to efficiently manage tryptophan levels. The operon includes a leader sequence (trpL) that plays a crucial role in the attenuation process.

Mutations and Their Effects

Mutations are changes in the DNA sequence that can affect gene function. In the context of the trp operon, a deletion mutation in the trpL region would eliminate the leader peptide and the regulatory sequences necessary for proper attenuation control. This could lead to continuous transcription of the operon, resulting in overproduction of tryptophan when it is not needed.