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.
Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
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Table of contents
- Ch. 1 - The Molecular Basis of Heredity, Variation, and Evolution64
- Ch. 2 - Transmission Genetics144
- Ch. 3 - Cell Division and Chromosome Heredity81
- Ch. 4 - Gene Interaction87
- Ch. 5 - Genetic Linkage and Mapping in Eukaryotes103
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages73
- Ch. 7 - DNA Structure and Replication71
- Ch. 8 - Molecular Biology of Transcription and RNA Processing79
- Ch. 9 - The Molecular Biology of Translation110
- Ch. 10 - Eukaryotic Chromosome Abnormalities and Molecular Organization100
- Ch. 11 - Gene Mutation, DNA Repair, and Homologous Recombination86
- Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage90
- Ch. 13 - Regulation of Gene Expression in Eukaryotes38
- Ch. 14 - Analysis of Gene Function via Forward Genetics and Reverse Genetics72
- Ch. 15 - Recombinant DNA Technology and Its Applications69
- Ch. 16 - Genomics: Genetics from a Whole-Genome Perspective49
- Ch. 17 - Organelle Inheritance and the Evolution of Organelle Genomes27
- Ch. 18 - Developmental Genetics43
- Ch. 19 - Genetic Analysis of Quantitative Traits66
- Ch. 20 - Population Genetics and Evolution at the Population, Species, and Molecular Levels105
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172Not the one you use?Change textbook
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Sanders 3rd EditionCh. 12 - Regulation of Gene Expression in Bacteria and BacteriophageProblem 25i
Sanders 3rd EditionCh. 12 - Regulation of Gene Expression in Bacteria and BacteriophageProblem 25iChapter 12, Problem 25i
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.
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Understand the role of the trpL region: The trpL region is part of the leader sequence in the trp operon. It contains a short coding sequence for a leader peptide and plays a critical role in attenuation, a regulatory mechanism that controls transcription of the trp operon based on tryptophan levels.
Recognize the mechanism of attenuation: Attenuation relies on the formation of secondary structures (stem-loops) in the mRNA transcript of the trpL region. These structures depend on ribosome activity during translation of the leader peptide. If tryptophan levels are high, the ribosome quickly translates the leader peptide, allowing the formation of a terminator stem-loop that halts transcription. If tryptophan levels are low, the ribosome stalls, allowing the formation of an anti-terminator stem-loop that permits transcription of the operon.
Analyze the effect of deleting the trpL coding sequence: If the entire coding sequence of trpL is deleted, the leader peptide cannot be synthesized. Without the leader peptide, the ribosome cannot stall or progress based on tryptophan levels, disrupting the formation of the attenuation-related stem-loops.
Predict the likely outcome: The deletion of the trpL coding sequence would likely abolish attenuation control. Transcription of the trp operon genes would proceed regardless of tryptophan levels, as the regulatory mechanism dependent on ribosome activity and stem-loop formation is no longer functional.
Summarize the reasoning: The trpL coding sequence is essential for attenuation control because it enables the ribosome to respond to tryptophan levels and influence stem-loop formation. Its deletion removes this regulatory capability, leading to constitutive transcription of the trp operon.
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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 in the leader region (trpL) determines whether transcription continues or is terminated prematurely. This process is sensitive to the levels of tryptophan, allowing the cell to respond to nutrient availability by adjusting gene expression.
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Trp Attenuation
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, allowing the cell to efficiently manage resources based on tryptophan availability. The operon includes a leader sequence (trpL) that plays a crucial role in the attenuation mechanism.
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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, regardless of tryptophan levels, potentially resulting in overproduction of tryptophan-synthesizing enzymes.
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Related Practice
Textbook Question
Suppose that base substitution mutations sufficient to eliminate the function of the operator regions listed below were to occur. For each case, describe how transcription or life cycle would be affected.
OR1 mutation in λ phage
Textbook Question
Suppose that base substitution mutations sufficient to eliminate the function of the operator regions listed below were to occur. For each case, describe how transcription or life cycle would be affected.
lacO mutation in E. coli
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.
Two nucleotides are inserted immediately following the polypeptide start codon.
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.
Twenty nucleotides are inserted into the trpL region immediately after the polypeptide stop codon.
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.
The eight uracil nucleotides immediately following region 4 are deleted.
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