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 start (AUG) codon of the trpL polypeptide is deleted.

Verified step by step guidance

1. Understand the role of the trpL region in the trp operon: The trpL region contains a leader peptide sequence that plays a crucial role in the attenuation mechanism of the trp operon, which regulates the transcription of genes involved in tryptophan synthesis.
2. Recognize the importance of the start codon: The start codon (AUG) is essential for the initiation of translation of the leader peptide. Without it, the ribosome cannot begin translating the trpL mRNA into the leader peptide.
3. Consider the impact of the mutation: If the start codon is deleted, the ribosome cannot initiate translation of the leader peptide. This means that the ribosome will not stall at the tryptophan codons in the leader sequence, regardless of tryptophan levels.
4. Analyze the effect on attenuation: Without translation of the leader peptide, the ribosome does not influence the formation of the attenuator structure in the mRNA. This could lead to the formation of the terminator hairpin structure, causing premature termination of transcription.
5. Conclude the likely outcome: The deletion of the start codon in the trpL region would likely result in constitutive attenuation, where transcription of the trp operon is prematurely terminated, regardless of tryptophan availability, potentially reducing the expression of downstream genes.

Key Concepts

Attenuation in Gene Regulation

Attenuation is a regulatory mechanism in prokaryotes, particularly in the trp operon, that controls gene expression based on the availability of tryptophan. It involves the formation of specific RNA structures during transcription that can either promote or inhibit the continuation of transcription, depending on the cellular conditions.

trp Operon Structure

The trp operon is a cluster of genes in bacteria that encode enzymes for tryptophan biosynthesis. It includes regulatory regions such as the trpL leader sequence, which plays a crucial role in attenuation by sensing tryptophan levels and influencing the formation of transcriptional terminators or antiterminators.

Impact of Mutations on Protein Function

Mutations, such as the deletion of the start codon (AUG) in the trpL region, can significantly affect protein synthesis. In this case, the absence of the start codon would prevent the translation of the trpL peptide, disrupting the feedback mechanism that regulates the trp operon and potentially leading to unregulated transcription of tryptophan biosynthetic genes.