In E. coli, transcription of the lac operon would be increased by:Group of answer choicesA missense mutation that disrupts the activity of the catabolite activator protein (CAP).A mutation in the lacI repressor gene that increases the affinity of the repressor for allolactose.A mutation in the lacI repressor gene that increases the affinity of the repressor for the lac operator.The presence of glucose in the growth medium.
Question
In E. coli, transcription of the lac operon would be increased by:Group of answer choicesA missense mutation that disrupts the activity of the catabolite activator protein (CAP).A mutation in the lacI repressor gene that increases the affinity of the repressor for allolactose.A mutation in the lacI repressor gene that increases the affinity of the repressor for the lac operator.The presence of glucose in the growth medium.
Solution
The transcription of the lac operon in E. coli would be increased by a mutation in the lacI repressor gene that increases the affinity of the repressor for the lac operator.
Here's why:
The lac operon is a set of genes in E. coli that are responsible for the metabolism of lactose. The operon is regulated by several factors, including the lacI repressor protein and the catabolite activator protein (CAP).
The lacI repressor protein binds to the lac operator, a DNA sequence within the lac operon, and prevents transcription of the operon. If a mutation increases the affinity of the lacI repressor for the lac operator, it would bind more tightly to the operator, preventing other proteins from initiating transcription. However, in the presence of allolactose, the repressor changes shape and can no longer bind to the operator, allowing transcription to proceed.
Therefore, a mutation that increases the affinity of the lacI repressor for the lac operator would increase transcription of the lac operon, as it would be more likely to be removed in the presence of allolactose.
On the other hand, a missense mutation that disrupts the activity of CAP would decrease transcription of the lac operon, as CAP is a positive regulator that enhances transcription in the absence of glucose. Similarly, the presence of glucose in the growth medium would decrease transcription, as it would lead to a decrease in the levels of cyclic AMP, the molecule that binds to CAP to activate it. Finally, a mutation that increases the affinity of the repressor for allolactose would not increase transcription, as it would simply make the repressor more likely to be inactivated in the presence of allolactose.
Similar Questions
Lactose or its analogues act as positive regulators of Lac operon by:Select one:a. Attaching to I gene and preventing its expressionb. Binding to repressor subunits so that the repressor cannot attached to operator locus.c. Increasing the synthesis of catabolic gene activator protein.d. Attaching to promoter region and facilitating the biding of RNA polymerase
The lac operon in E. coli is a coordinately controlled set of genes required for lactose metabolism. The operon and its associated regulatory sequences are shown in the following diagram.Two parallel horizontal lines are shown with a break between the first segment and the second segment. The first segment has a box labeled promoter and a box labeled lacI followed by an unlabeled black box. The second segment begins with an unlabeled black box, followed by a box labeled CAP site, a box labeled promoter, a box labeled operator and then 3 boxes with a bracket above them with the caption structural genes. The 3 boxes are labeled lacZ, lacY and lacA.The function of each locus shown in the diagram is listed in the table below.Part FunctionPromoter Binding site for RNA polymeraselacI Gene encoding the lac repressor proteinCAP site Binding site for the catabolite activator proteinOperator Binding site for the lac repressor proteinlacZ Gene encoding the beta-galactosidase proteinlacY Gene encoding the lactose permease proteinlacA Gene encoding the galactoside transacetylase proteinThe activity of the lac operon is influenced by the availability of lactose and glucose in the cellular environment. In the presence of lactose, the lac repressor protein is released from the operator, which allows the structural genes to be transcribed at a low level. If glucose (the preferred carbon source) is absent during this time, the catabolite activator protein binds to the CAP site, causing the structural genes to be transcribed at a higher level.Which of the following is the most likely result of a mutation in the lac repressor protein that prevents binding to the operator?Choose 1 answer:Choose 1 answer:(Choice A, Checked) The catabolite activator protein will not bind to the CAP site, even in the absence of glucose.AThe catabolite activator protein will not bind to the CAP site, even in the absence of glucose.(Choice B) The lacI gene will be highly expressed, even in the presence of glucose.BThe lacI gene will be highly expressed, even in the presence of glucose.(Choice C) The structural genes will not be transcribed, even in the presence of lactose.CThe structural genes will not be transcribed, even in the presence of lactose.(Choice D) The lactose permease protein will be produced, even in the absence of lactose.DThe lactose permease protein will be produced, even in the absence of lactose.
The lac operon system, first described by Jacob and Monod, regulates lactose metabolism in . The is composed of a gene encoding a protein that normally keeps this operon in the position. Within the , the repressor binds to the , blocking transcription of structural genes needed for lactose metabolism. When is added to a cell's environment, it binds the repressor freeing the operator segment of the DNA. is now able to bind to the promoter, transcribing all three structural genes needed for lactose catabolism. When lactose again becomes depleted in the cell, the repressor binds to the operator blocking additional synthesis of enzymes from the .
A mutation occurs in the operator site within the lac operon of E.coli which prevents binding to the operator of the protein encoded by the lac i gene. What will be the likely effect of this mutation (assume glucose to be absent)? ß-galactosidase will be produced only in the presence of galactose ß-galactosidase will be produced only in the absence of lactose ß-galactosidase will not be produced in significant levels regardless of the presence of lactose ß-galactosidase will be produced continuously regardless of the presence of lactose ß-galactosidase will be produced only in the presence of lactose
Ask StudybuddyThe activation of the lac operon requires a signaling molecule regulated by what monosaccharide? An increase in the synthesis of tryptophane regulated by Lac z A decrease in cAMP synthesis regulated by an increase in glucose An increase in cAMP regulated by a decrease of glucose A decrease in tryptophane that activates cAMP synthesis An increase in lactose that activates cAMP synthesis
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