Concept explainers
To determine: The
Introduction: A repressor molecule or protein prevents the RNA polymerase from binding to the promoter region and thus, prevents the expression of genes.
Explanation of Solution
The phenotype of a repressor mutation in which binding of DNA is prevented would be the expression of the genes which facilitate lactose
To determine: The phenotype of a repressor mutation that prevents DNA binding and an operator mutation that prevents repressor binding.
Introduction: In molecular biology, operator is a genetic sequence which is responsible for facilitating the transcribing proteins to bind to the DNA sequence being transcribed.
Explanation of Solution
Mutation in the operator or inducer that prevents the binding of the repressor would allow the operator to bing to the DNA all the time and the genes for lactose metabolism would not get expressed. This is because the RNA polymerase would bind to the DNA and transcription would proceed. This is in contrast to the phenotype expressed when mutation in the repressor would prevent transcription.
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Chapter 16 Solutions
2 SEM CARDLESS ACC W/RAVEN TEXT
- Many transcriptional activators are proteins with a DNA-binding domain (DBD) and an activation domain (AD). Explain how each domain contributes to transcriptional initiation. Would you expect repressors to also have each of these domains?arrow_forwardThe lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products. These mutations include: I - = produces a repressor protein that cannot bind to the operator region IS = produces a repressor protein that cannot be removed from the operator region OC = cannot bind a repressor protein Z - = produces a defective (non-functioning) β-galactosidase enzyme + = wild type Detail the functionality of the lac operon under the following genetic and cellular conditions. You do not need to consider the role of CAP in your analysis. Genes Repressed (yes/no) Constitutive (yes/no) I+ OC Z+ I+ O+ Z+ (Lactose present) I- O+ Z+arrow_forwardThe lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products. These mutations include: I - = produces a repressor protein that cannot bind to the operator region IS = produces a repressor protein that cannot be removed from the operator region OC = cannot bind a repressor protein Z - = produces a defective (non-functioning) β-galactosidase enzyme + = wild type Detail the functionality of the lac operon under the following genetic and cellular conditions. You do not need to consider the role of CAP in your analysis. Genes Repressed (yes/no) Constitutive (yes/no) IS O+ Z+ IS OC Z+arrow_forward
- At 2:00 pm, you measured intracellular arginine at 100M. After addition of 200M of arginine to the cell, you, at 2:45 pm, measured intracellular arginine levels to be still at 100M. The most likely explanation is: Arginine bound to the active site of the repressor protein Arginine bound to the allosteric site of RNA polymerase Arginine was in excess in the cell and acted as an inducer Arginine was in excess in the cell and bound to the operator Arginine bound to the allosteric site of the repressor proteinarrow_forwardWhat would happen to the regulation of the tryptophan operon in bacterial cells that express a mutant form of the tryptophan repressor that (1) cannot bind to DNA, (2) cannot bind tryptophan, or (3) binds to DNA even in the absence of tryptophan?arrow_forwardWhat is the probability that the palindromic symmetry of the trp repressor target DNA sequence is merely accidental?arrow_forward
- If a gene is repressible and under positive control, what kind of effector molecule and regulatory protein are involved in its regulation? Explain how the binding of the effector molecule affects the regulatory protein.arrow_forwardIf a repressor prevents TFIID from binding to the TATA box, why does this inhibit transcription?arrow_forwardIf the lacl gene is mutated so that the repressor protein no longer binds to lactose, what will be the effect on the expression of B-galactosidase in lactose's presence and absence? Explain. If the promoter for lacl is mutated so that the expression of the repressor increases, what will be the effect on the expression of B-galactosidase in the presence and absence of lactose? Explain. D. (Extremely tricky question!) Describe the behavior of the lac operon assuming that the lacl gene has been mutated so that the repressor now binds to DNA in the presence of lactose but cannot bind to DNA in the absence of lactose.arrow_forward
- which of the following correctly describes how protein kinase A can activate genes? A: nuclear protein kinase A is activated by cAMP to phosphorylate general transcription factors B: cytosolic protein kinase A is activated by cAMP to release the catalytic subunits, which move into the nucleus and phosphorylate CREB C: cytosolic protein kinase A is activated by cAMP to release the catalytic subunits, which move into the nucleus and phosphorylate general transcription factors D: G protein-coupled receptors may be desensitized by serine phosphorylationarrow_forwardWhat would happen if the operator sequence of the trp operon contained a mutation that prevented the repressor protein from binding to the operator? (Explain what would happen in both the presence and absence of tryptophan)arrow_forwardRefer to figure, which shows the distribution of histone H2A.Z on nucleosomes near a transcription start site. What experimental technique would have been used to generate the data for this figure? Briefly describe the operation of this technique.arrow_forward
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