Campbell Essential Biology with Physiology (5th Edition)
5th Edition
ISBN: 9780321967671
Author: Eric J. Simon, Jean L. Dickey, Jane B. Reece, Kelly A. Hogan
Publisher: PEARSON
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Chapter 11, Problem 13PS
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
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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
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+
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+
Chapter 11 Solutions
Campbell Essential Biology with Physiology (5th Edition)
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- You 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, answer the following questions Which operons would be functional under these conditions? 2. What repressors would be made? (NOTE: name the repressors using their gene names) 3.Which repressor(s) would be made in the inactive form? 4.Which repressor(s) would be made in the active form? 5.Which repressor(s) under these conditions can bind the operator sequence? 6.Which repressor(s)under these conditions cannot bind the operator sequence?arrow_forwardMutations 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 attenuationarrow_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_forward
- Consider the trp operon found in E. coli. You have discovered a mutant strain of E.coli that contains a mutation in its trpR gene. This mutation prevents the trpR protein from binding to its small effector molecule. What would happen if both the wild type and mutant bacteria were put in an environment that contained lots of tryptophan? The normal (wild type) bacteria would have (i)________expression of the trp operon while the mutant bacteria would have (ii) _________ expression of the trp operon. A) (i) high (ii) high B) (i) low (ii) low C) (i) high (ii) low D) (i) low (ii) higharrow_forward. In the tryptophan operon of E. coli, what happens when tryptophan levels get too high? tryptophan is removed from its co-repressor, causing it to detach from the operator tryptophan is removed from its co-repressor, causing it to attach to the operator tryptophan is bound to its co-repressor, causing it to detach from the operator tryptophan is bound to its co-repressor, causing it to attach to the operator all of the above occur at equal rates when tryptophan levels get too higharrow_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, answer the following questions using the dropdown menus provided in Canvas. Which operons would be functional under these conditions? What repressors would be made? (NOTE: name the repressors using their gene names) Which repressor(s) would be made in the inactive form? Which repressor(s) would be made in the active form? Which repressor(s) under these conditions can bind the operator sequence?arrow_forward
- 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.arrow_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, answer the following questions using the dropdown menus provided in Canvas. Which operons would be functional under these conditions? What repressors would be made? (NOTE: name the repressors using their gene names) Which repressor(s) would be made in the inactive form? Which repressor(s) would be made in the active form? Which repressor(s) under these conditions can bind the operator sequence? Which repressor(s)under these conditions cannot bind the operator sequence? What effect does lactose have on the bacterial cell’s lac operon? What does the absence of glucose do to the bacterial cell? You now add tryptophan to the cell. What would happen to the bacterial cell and its trp operon? What kind of regulation does lactose provide to an operon’s…arrow_forwardAll of the following statements about the repressor of the lac operon of E. coli are true EXCEPT which one? O A. The repressor is the product of a regulatory gene i The repressor binds to the operator region of the DNA of the lac OB. operon. The repressor is a protein. OC. The repressor interacts with the operator in such a way as to OD. prevent translation of beta-galactosidase. The repressor can combine with lactose to form a OE. complex that will no longer bind to the operator region. QUESTION 32 The amino acid which is a precursor of serotonin is Histidine OA. O B. Tyrosine O C. Glutamate D. Tryptophan O E. none of the abovearrow_forward
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