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. Two nucleotides are inserted immediately following the polypeptide start codon.

Key Concepts

Attenuation Control

Attenuation is a regulatory mechanism in prokaryotic gene expression, particularly in the trp operon, where the formation of specific RNA structures determines whether transcription continues or terminates. In the trp operon, the presence of tryptophan influences the formation of a transcription terminator or an anti-terminator, thereby controlling the synthesis of enzymes involved in tryptophan biosynthesis.

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 respond to tryptophan levels. When tryptophan is abundant, the operon is repressed, while low levels of tryptophan promote transcription.

Mutations and Their Effects

Mutations, such as insertions or deletions of nucleotides, can significantly impact gene function by altering the protein sequence or regulatory elements. In the context of the trpL region, an insertion of two nucleotides after the start codon could disrupt the formation of RNA structures necessary for proper attenuation, potentially leading to either increased or decreased transcription of the trp operon, depending on how the mutation affects the ribosome's interaction with the mRNA.