Textbook Question
The trpL region contains four repeated DNA sequences that lead to the formation of stem-loop structures in mRNA. What are these stem-loop structures, and how do they affect transcription of the structural genes of the trp operon?
Ch. 12 - Regulation of Gene Expression in Bacteria and Bacteriophage
Sanders3rd EditionGenetic Analysis: An Integrated ApproachISBN: 9780135564172
Not the one you use?Change textbookSelect a different textbook
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
All textbooks
Sanders 3rd EditionCh. 12 - Regulation of Gene Expression in Bacteria and BacteriophageProblem 10
Sanders 3rd EditionCh. 12 - Regulation of Gene Expression in Bacteria and BacteriophageProblem 10Chapter 12, Problem 10
How would a cap⁻ mutation that produces an inactive CAP protein affect transcriptional control of the lac operon?
Verified step by step guidance1
Understand the role of the CAP protein in the lac operon: CAP (catabolite activator protein) is a regulatory protein that facilitates the binding of RNA polymerase to the promoter of the lac operon, enhancing transcription. CAP requires cAMP to bind to the DNA at the CAP site.
Recognize the impact of a cap⁻ mutation: A cap⁻ mutation results in an inactive CAP protein. This means that CAP cannot bind to the CAP site on the DNA, even in the presence of cAMP.
Analyze the effect on transcription: Without CAP binding, RNA polymerase has difficulty binding efficiently to the promoter of the lac operon. This leads to reduced transcription of the operon, even when lactose is present and glucose levels are low.
Consider the physiological context: The lac operon is normally activated when glucose is scarce and lactose is available. The cap⁻ mutation disrupts this regulatory mechanism, leading to poor expression of the lac operon regardless of glucose levels.
Conclude the overall effect: The cap⁻ mutation results in a significant reduction in the transcriptional activation of the lac operon, impairing the cell's ability to metabolize lactose efficiently under conditions where it would normally do so.
Verified video answer for a similar problem:
This video solution was recommended by our tutors as helpful for the problem above.
Video duration:
4mWas this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
CAP Protein Function
The CAP (catabolite activator protein) is a transcription factor that enhances the expression of certain genes, including the lac operon, in response to low glucose levels. When glucose is scarce, CAP binds to cyclic AMP (cAMP), forming a complex that promotes RNA polymerase binding to the promoter of the lac operon, facilitating transcription.
Recommended video:
Guided course
05:05
Proteins
Lac Operon Structure
The lac operon is a set of genes in E. coli that are involved in the metabolism of lactose. It consists of three structural genes (lacZ, lacY, and lacA) and regulatory elements, including the promoter and operator. The operon is typically off when glucose is present but can be activated in the absence of glucose, allowing the bacteria to utilize lactose as an energy source.
Recommended video:
Guided course
04:27Lac Operon Overview
Transcriptional Control Mechanisms
Transcriptional control mechanisms regulate gene expression in response to environmental changes. In the case of the lac operon, the presence of glucose inhibits cAMP production, leading to reduced CAP-cAMP complex formation. A cap⁻ mutation that produces an inactive CAP protein would prevent this activation, resulting in decreased transcription of the lac operon, even when lactose is available.
Recommended video:
Guided course
09:16Eukaryotic Transcription
Related Practice
Textbook Question
The CAP binding site in the lac promoter is the location of positive regulation of gene expression for the operon. Identify what binds at this site to produce positive regulation, under what circumstances binding occurs, and how binding exerts a positive effect.
Textbook Question
What role does cAMP play in transcription of lac operon genes? What role does CAP play in transcription of lac operon genes?
Textbook Question
Explain the circumstances under which attenuation of operon gene expression is advantageous to a bacterial organism. Would you expect attenuation to be found in a single-celled eukaryote? In a multicelled eukaryote?
Textbook Question
Consider the transcription of genes of the lac operon under two conditions: (1) when both glucose and lactose are present and (2) when glucose is absent and lactose is present. Describe the comparative levels of transcription of lac operon genes under these conditions, and explain the molecular basis for the difference.
Textbook Question
Describe the lytic and lysogenic life cycles of λ bacteriophage. What roles do λ repressor and Cro protein play in controlling transcription from PR and PRM, and how are these roles linked to lysis and lysogeny?
3
views