Brock Biology of Microorganisms (15th Edition)
15th Edition
ISBN: 9780134261928
Author: Michael T. Madigan, Kelly S. Bender, Daniel H. Buckley, W. Matthew Sattley, David A. Stahl
Publisher: PEARSON
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Chapter 6, Problem 2AQ
Most of the regulatory systems described in this chapter employ regulatory proteins. However, regulatory RNA is also important. Describe how one could achieve negative control of the lac operon using either of two different types of regulatory RNA.
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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?
Supply the words “off" or “on" in the blanks below:
In an inducible operon, transcription is normally
and must be turned
In a repressible operon, transcription is normally
and must be turned
Briefly describe the overall function of the structural genes in the lac operon.
Briefly describe the overall function of the structural genes in the trp operon.
For the following descriptions of the bacterial lac operon, determine if lactose is present
(P) or absent (A).
The repressor is bound to the operator.
The repressor is inactive.
RNA polymerase transcribes the structural genes.
Allolactose is bound to the repressor
For the following descriptions of the bacterial trp operon, determine if tryptophan levels
are high (H) or low (L).
The repressor is bound to the operator.
The repressor is inactive.
RNA polymerase transcribes the structural genes.
Tryptophan is bound to the repressor.
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 control
Chapter 6 Solutions
Brock Biology of Microorganisms (15th Edition)
Ch. 6.1 - What is protein domain?Ch. 6.1 - Why are most DMA-binding proteins specific to...Ch. 6.1 - Describe why a protein that binds to a specific...Ch. 6.2 - Why is negative control so named?Ch. 6.2 - How does a repressor inhibit the synthesis of a...Ch. 6.2 - Induction is considered the opposite of enzyme...Ch. 6.3 - Prob. 1MQCh. 6.3 - Prob. 2MQCh. 6.3 - What is the difference between an operon and a...Ch. 6.4 - Prob. 1MQ
Ch. 6.4 - Prob. 2MQCh. 6.4 - Explain how the lac operon is both positively and...Ch. 6.4 - Prob. 1CRCh. 6.5 - What is the major difference between...Ch. 6.5 - How do transcriptional activators in Archaea often...Ch. 6.5 - Explain how the Pyrococcus furiosus TrmBL1...Ch. 6.5 - Prob. 1CRCh. 6.6 - What are kinases and what is their role in...Ch. 6.6 - Prob. 2MQCh. 6.6 - Prob. 1CRCh. 6.7 - What are the primary response regulator and the...Ch. 6.7 - Why is adaptation during chemotaxis important?Ch. 6.7 - How does the response of the chemortaxis system to...Ch. 6.7 - Adaptation allows the mechanism controlling...Ch. 6.8 - What advantage do quorum-sensing systems confer on...Ch. 6.8 - Prob. 2MQCh. 6.8 - Prob. 3MQCh. 6.8 - How can quorum sensing be considered a regulatory...Ch. 6.9 - Which Escherichia coli genes are activated and...Ch. 6.9 - Prob. 2MQCh. 6.9 - What are some other conditions that trigger the...Ch. 6.9 - Explain the sequence of molecular events that...Ch. 6.10 - Prob. 1MQCh. 6.10 - Prob. 2MQCh. 6.10 - Prob. 3MQCh. 6.10 - Prob. 1CRCh. 6.11 - Prob. 1MQCh. 6.11 - Prob. 2MQCh. 6.11 - Prob. 3MQCh. 6.11 - What are the mechanisms by which regulation by...Ch. 6.12 - What happens when a riboswitch binds the small...Ch. 6.12 - What are the major differences between a repressor...Ch. 6.12 - What is the mechanism by which a riboswitch...Ch. 6.13 - Why does attenuation control not occur in...Ch. 6.13 - Prob. 2MQCh. 6.13 - Prob. 1CRCh. 6.14 - What is feedback inhibition?Ch. 6.14 - Prob. 2MQCh. 6.14 - Prob. 3MQCh. 6.14 - Describe how feedback inhibition is reversible.Ch. 6.15 - What types of covalent modifications commonly...Ch. 6.15 - Prob. 2MQCh. 6.15 - Explain the role of an anti-sigma factor.Ch. 6.15 - Which nucleotides are commonly used to covalently...Ch. 6 - What would happen to regulation from a promoter...Ch. 6 - Most of the regulatory systems described in this...Ch. 6 - Many amino acid biosynthetic operons under...Ch. 6 - How would you design a regulatory system to make...
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- For the following questions, describe the expression levels of the structural genes in the Lac operon under the conditions described. In the absence of lactose, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of lactose, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of lactose and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of lactose and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of lactose and the lacI repressor gene is mutated such that the repressor protein…arrow_forwardFor the following questions, describe the expression levels of the structural genes in the Trp operon under the conditions described. In the absence of tryptophan, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of tryptophan, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of tryptophan and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of tryptophan and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of tryptophan and the trpR repressor gene is mutated such that the…arrow_forwardFor the following questions, describe the expression levels of the structural genes in the Trp operon under the conditions described. In the absence of tryptophan, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the presence of tryptophan, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"] In the absence of tryptophan and the promoter sequence was mutated such that the RNA polymerase can no longer bind, the structural genes will:[ Select ] ["No longer be expressed", "Be constantly expressed", "Be deleted from the operon"]arrow_forward
- Which of the following lac operon genotypes would allow for functional versions of all the structural enzymes of the lac operon to be expressed constitutively even in the absence of lactose? Group of answer choices I+ O+ Z+ Y+ A+ I- O+ Z- Y- A- I+ OC Z+ Y+ A+ IS O+ Z+ Y+ A+ I+ O+ Z- Y+ A+arrow_forwardIf glucose levels in the cell are high and 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?arrow_forwardA theoretical operon (theo) in E. coli contains several structural genes encoding enzymes that are involved sequentially in the biosynthesis of an amino acid. Unlike the lac operon, in which the repressor gene is separate from the operon, the gene encoding the regulator molecule is contained within the theo operon. When the end product (the amino acid) is present, it combines with the regulator molecule, and this complex binds to the operator, repressing the operon. In the absence of the amino acid, the regulatory molecule fails to bind to the operator, and transcription proceeds. Characterize this operon, then consider the following mutations, as well as the situation in which the wild-type gene is present along with the mutantgene in partially diploid cells (F¿):(a) Mutation in the operator region.(b) Mutation in the promoter region.(c) Mutation in the regulator gene.In each case, will the operon be active or inactive in transcription, assuming that the mutation affects the…arrow_forward
- Examine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Promoter || Operator genC genB gen operon Regulator genAarrow_forwardExamine the following theoretical operon (gen) in E. coli which contains structural genes (genC, genB, genA) that are involved in amino acid biosynthesis. The gen operon also includes the gene encoding for the regulator molecule within it. When the amino acid that this operon helps synthesize is present, it binds to the regulator forming a complex which can bind to the operator region. Assume that the regulator molecule only binds to the operator in the presence of the amino acid. Question 1 Promoter Operator genC genB gen operon Regulator genA Transcription occurs when: A. The amino acid is not bound to the regulator, causing the regulator to bind to the operator. B. The amino acid is bound to the regulator, causing the regulator to bind to the operator. C. The amino acid is not bound to the regulator, causing the regulator to fail to bind to the operator. D. The amino acid is bound to the regulator, causing the regulator to fail to bind to the operator. E. The operon is…arrow_forwardImagine 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).arrow_forward
- A number of mutations affect the expression of the lac operon in E. coli. The genotypes of several E. coli strains are shown below. ("+" indicates a wild-type gene with normal function and "-" indicates a loss-of-function allele.) Please predict which of the following strains would have the highest beta-galactosidase enzyme activity, when grown in the lactose medium. O CAP+ r* p* o* z O CAP* I P* o* z* O CAP* r* P O* z* O CAP I P* O z*arrow_forwardThe streptolysin S toxin made by S. pyogenes is encoded by a 9-gene operon, sagABCDEFGHI. Thinking about what a 3-line diagram would look like for this operon, answer the following questions. Write numeric answers only. For example, if your answer is 6 promoters, write only 6. 1) How many promoters control the expression of these genes? 2) How many locations does RNA Polymerase bind to get full expression of these genes? 3) How many ribosome binding sites are needed for full protein expression? 4) How many start codons will be needed for full protein expression? 5) How many mRNA strands will be produced with full operon expression? 6) How many proteins will be produced with full protein expression? 1arrow_forwardWhat would happen if the operator sequence of the lac operon contained a mutation that prevented the repressor protein from binding the operator? (Explain what would happen both in the presence and absence of lactose)arrow_forward
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