Campbell Biology: Concepts & Connections (9th Edition)
9th Edition
ISBN: 9780134296012
Author: Martha R. Taylor, Eric J. Simon, Jean L. Dickey, Kelly A. Hogan, Jane B. Reece
Publisher: PEARSON
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Chapter 11, Problem 9TYK
Mutations can alter the function of the lac operon (see Module 11.1). Predict how the following mutations would affect the function of the operon in the presence and absence of lactose:
a. Mutation of regulatory gene; repressor cannot bind to lactose.
b. Mutation of operator; repressor will not bind to operator.
c. Mutation of regulatory gene; repressor will not bind to operator.
d. Mutation of promoter; RNA polymerase will not attach to promoter.
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Students have asked these similar questions
a. What is the function of operons in bacterial gene regulation?
b. Describe how a bacterial operon can be regulated by repressible proteins (such as the tryptophan operon). Include in your description both the “on” and “off” states of the operon. Key elements of your diagram should include: Co-repressor, Genes, mRNA, Operator, Operon, Promoter, Repressor, RNA polymerase.
Study the depiction of the lac operon in Figure 11.2. Normally, the genes are turned off when lactose is not present. Lactose activates the genes, which code for enzymes that enable the cell to use lactose. Mutations can alter the function of this operon. Predict how the following mutations would affect the function of the operon in the presence and absence of lactose: a. mutation of regulatory gene; repressor will not bind to lactose b. mutation of operator; repressor will not bind to operator c. mutation of regulatory gene; repressor will not bind to operator d. mutation of promoter; RNA polymerase will not attach to promoter
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
Chapter 11 Solutions
Campbell Biology: Concepts & Connections (9th Edition)
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- Consider the lac operon of E. coli. Specifically, explain the following: a. Describe the overall chromosomal structure/organization of the operon, indicating the location and function of the regulatory regions and the structural genes. b. Is lac a catabolic or anabolic pathway? Explain. Is the operon inducible or repressible? Explain. c. Describe the mechanisms involved in negative control & positive controlarrow_forwardA 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 inhibitedarrow_forwardYou are growing E. coli in a laboratory in order to study their operons. The growth media you are using contains lactose, no glucose and no tryptophan. Using your knowledge of operons and their regulation a.Which operons would be functional under these conditions? b.What repressors would be made? (NOTE: name the repressors using their gene names) c.Which repressor(s) would be made in the inactive form? d.Which repressor(s) would be made in the active form? e.Which repressor(s) under these conditions can bind the operator sequence? f.Which repressor(s)under these conditions cannot bind the operator sequence?arrow_forward
- The map of the lac operon is: POZY The promoter (P) region is the start site of transcription through the binding of the RNA polymerase molecule before actual MRNA production. Mutationally altered promoters (P') cannot bìnd the RNA polymerase molecule. Certain predictions can be made about the effect of P mutations. Use your knowledge of the lactose system to complete the table below. Insert a "+" where enzyme is produced and a "-" where enzyme is not produced. Indicate whether the partial diploid strain is lac* (able to grow on lactose-only medium) or lac( cannot grow in lactose medium). B-Galactosidase Permease Phenotype (Lac or Number Genotype No Lactose Lactose No Lactose Lactose Lac) P*O*Z*Y# Example lac+ I*p*O*z*Y* a Ip*o+z*Y* I*p*oCz*Y C I*p*o+z*Yarrow_forwardImagine this scenario: In E.coli the Operon X encodes for Proteins Y, X and Z. Proteins Y, X and Z are required for growth in the presence of Drug A. Outline the experiments that you would conduct to assess whether Protein B represses the transcription of Operon X in the absence of Drug A. Things to consider: 1. Transcription of Operon X 2. Mutations 3. Chromatin structurearrow_forwardMutations in the genes of the lac operon might affect the regulation of β-galactosidase synthesis. For each mutation listed below, indicating whether β-galactosidase would be regulated normally, always ON or always OFF. a. Mutation in operator site prevents repressor binding b. Mutation in lacIgene prevents repressor from binding operator c. Mutation in lacIgene prevents repressor from binding allolactose d. Nonsense mutation in lacZgenerearrow_forward
- Control of the trp operon relies on which of the following: a. High levels of tryptophan causing a pause (but not termination) in transcription b. Low levels of tryptophan causing a pause (but not termination) in transcription c. Allolactose binding to the inhibitor to prevent it from binding to the promoter d. Tryptophan binding to the inhibitor to prevent it from binding to the promoterarrow_forward4) Suppose you have an E. coli in which the gene that codes for the lac repressor protein has been mutated in such a way that the protein produced can bind to both lactose and DNA (at its specific binding site in the lac operon promoter) simultaneously. What effect, if any, would this have on regulation of expression of the lac operon? Briefly (1 sentence) explain why you would predict the effect or lack of effect this mutation would have.arrow_forwardIn the regulation of the tryophan operon in bacteria, the co-occurence of transcription and translation plays a key role regulating full activation of operon expression. Diagram and explain how during the conditions of high tryptophan concentration this system regulates the expression of genes in the operon.arrow_forward
- When iron is scarce, some bacteria can stop synthesis of all enzymes that require iron (Fe3+), such as superoxide dismutase (SOD). Which of the following accurately describes a mechanism for this regulation? Mark all that apply. A. Regulation occurs by an inducible operon B. When absent, the lack of iron causes the repressor to deactivate and block the promoter region for these genes C. Regulation occurs by a repressible operon D. When present, iron binds and activates the repressor proteinarrow_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
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