Textbook Question
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.
Region 3 is deleted.
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12. Gene Regulation in Prokaryotes
Tryptophan Operon and Attenuation
3:04 minutesProblem 25g
Textbook Question
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.
Ten nucleotides are inserted between regions 2 and 3 of trpL.
Verified step by step guidance1
Understand the trp operon and attenuation mechanism: The trp operon in *E. coli* is regulated by attenuation, which involves the formation of secondary RNA structures in the leader region (trpL). These structures depend on the interaction of regions 1, 2, 3, and 4 of the trpL mRNA. Specifically, the pairing of regions 2 and 3 prevents the formation of the terminator structure (regions 3 and 4 pairing), allowing transcription to continue.
Analyze the mutation: The problem states that 10 nucleotides are inserted between regions 2 and 3 of the trpL region. This insertion could disrupt the ability of regions 2 and 3 to base-pair due to the increased distance between them.
Predict the effect on attenuation: If regions 2 and 3 cannot pair effectively, the anti-terminator structure (formed by regions 2 and 3) may not form. This would allow regions 3 and 4 to pair instead, forming the terminator structure, which halts transcription of the trp operon genes.
Consider the physiological consequences: The inability to form the anti-terminator structure means that transcription of the trp operon genes would be prematurely terminated, even under conditions of low tryptophan. This would reduce the cell's ability to synthesize tryptophan when it is needed.
Summarize the reasoning: The insertion of 10 nucleotides between regions 2 and 3 likely disrupts attenuation control by preventing the formation of the anti-terminator structure. This would lead to constitutive termination of transcription, regardless of tryptophan levels, impairing the operon's function.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Attenuation Control
Attenuation control is a regulatory mechanism in prokaryotic gene expression, particularly in the trp operon, where the formation of specific RNA structures determines whether transcription will continue or terminate. This process relies on the interaction between the ribosome and the mRNA, allowing the cell to respond to the availability of tryptophan by adjusting gene expression accordingly.
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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 conserve resources by halting transcription when tryptophan is abundant, thus preventing unnecessary production of enzymes.
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Mutations and Their Effects
Mutations, such as insertions or deletions in the DNA sequence, can significantly impact gene function and regulation. In the context of the trp operon, an insertion of ten nucleotides between regions 2 and 3 of the trpL region could disrupt the formation of the necessary RNA structures for proper attenuation, potentially leading to altered levels of tryptophan synthesis depending on the new RNA folding patterns.
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