Mutations may have an effect on the expression of the lac operon and the trp operon. Would the following mutations have a cis- or transeffect on the expression of the protein-encoding genes in the operon? A. A mutation in the operator site that prevents lac repressor from binding to it B. A mutation in the lacI gene that prevents lac repressor from binding to DNA C. A mutation in the trpL gene that prevents attenuation

Mutations may have an effect on the expression of the lac operon and the trp operon. Would the following mutations have a cis- or transeffect on the expression of the protein-encoding genes in the operon? A. A mutation in the operator site that prevents lac repressor from binding to it B. A mutation in the lacI gene that prevents lac repressor from binding to DNA C. A mutation in the trpL gene that prevents attenuation

Biology (MindTap Course List)

11th Edition

ISBN:9781337392938

Author:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Publisher:Eldra Solomon, Charles Martin, Diana W. Martin, Linda R. Berg

Chapter14: Gene Regulation

Section: Chapter Questions

Problem 9TYU: A mutation that inactivates the repressor gene of the lac operon results in (a) the continuous...

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A mutation that inactivates the repressor gene of the lac operon results in (a) the continuous transcription of the structural genes (b) no transcription of the structural genes (c) the binding of the repressor to the operator (d) no production of RNA polymerase (e) no difference in the rate of transcription
If the above gene is one of the three structural genes of the lac operon that codes for the protein/ enzyme responsible for breaking lactose into two molecules of simple sugars, what triggers the activation of this gene? a. Absence of Inhibitory protein b. Presence of lactose c. Absence of lactose d. Presence of Inhibitory protein e. Absence of Regulatory protein
A mutation in the operator region of the trp operon can prevent the trp repressor from binding to this operator. When these mutant cells are placed in a solution containing chicken broth, which of the following happens? a. Tryptophan would bind to the repressor. b. The Repressor would bind to the operator irrespective of the presence of amino acids in the environment. c. The transcription of the trip operon would be inhibited. d. The transcription of the repressor protein is inhibited
A mutation in the repressor LacI causes it to lose the ability to bind its effector, allolactose. What will be the effect of this mutation in the presence of allolactose (assume glucose is absent)? a) LacI cannot bind to the lac operator (lacO) and transcription of the lac operon is blockedb) LacI is permanently bound to the lac operator (lacO) and transcription of the lac operon is blocked c) LacI cannot bind to the lac operator (lacO) and transcription of the lac operon increasesd) LacI is permanently bound to the lac operator (lacO) and transcription of the lac operon increases
Imagine that a new strain of E. coli is discovered, and it contains the following novel genetic region including the lacI gene and the lac operon: *see image* Upstream of the promoter associated with the lac operon, there is a new operator element "Oν" (O-"nu"). This new operator has high sequence homology to O1, the DNA element that is bound with the highest affinity by the lac repressor. What would be the impact of this new genetic element regarding behavior of the operonin the absence (vs. the presence) of lactose and allolactose? Answer in terms of the protein levels of the lac repressor, as well as the proteins encoded by the genes lacZ/Y/A in the downstream region of the operon. Remember that proteins, once expressed/generated, will not persist forever, and that they have a natural lifetime (ending when they are degraded by the cell).
The 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+
The 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+
In the lac operon, the lacZ gene codes for an enzyme called ____________, which catalyze the breakdown of the sugar __________ into monosaccharides. This enzyme can also hydrolyze the sugar analog ____________, which produces blue pigments following its breakdown. Since the lac operon is not always on the bacterial cells, we add the chemical ________ which prevents the lac depressor from binding to the operators, leading to constitutive expression of the operon.
How does the repressor protein contribute to selective expression of the structural genes Z, Y, and A in the lac operon? The repressor protein is only expressed when lactose is present. The repressor is always expressed. It blocks transcription when lactose is present. The repressor is always expressed. It allows transcription when lactose is absent. The repressor is always expressed. It blocks transcription when lactose is absent. The repressor protein is only expressed when lactose is absent.
Which of the following statements about the trp operon is false? If a mutation in region 2 prevents the formation of the 2 + 3 loop in the 5’UTR transcription levels will increase. The trp operon is an example of negative repressible operon. Formation of the anti-terminator in the 5’UTR of the trp operon occurs when trp levels are low. In the presence of high trp-tRNA, the genes of the trp operon are not expressed. The role of trp is to bind to the repressor protein and activate it.
If glucose is not available, but lactose is available from the environment, what is the status of transcription of the lac operon genes? Explain your answer from both an evolutionary perspective and in terms of negative and positive regulation of the operon?
. In the lac operon of E. coli, if glucose levels increase while lactose levels decrease, what will happen in the regulation of genes controlling the enzymes needed to catabolize lactose? the lac operon will be activated due to cAMP-assisted CAP binding to a site near the promoter the lac operon will be activated due to CAP detachment from a site near the promoter the lac operon will be repressed due to cAMP-assisted CAP binding to a site near the promoter the lac operon will be repressed due to CAP detachment from a site near the promoter all of the above