Campbell Biology in Focus (2nd Edition)
2nd Edition
ISBN: 9780321962751
Author: Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Jane B. Reece
Publisher: PEARSON
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Chapter 15, Problem 4TYU
Summary Introduction
Introduction:
Operon refers to the functional unit of the DNA (genomic). It consist of various genes that controls operon’s regulation. There are two types of operons; lac (lactose) and Trp (tryptophan).
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Which statement about the transcription attenuation mechanism is TRUE?
1.In some operons (e.g., the his operon), attenuation may be the only regulatory mechanism.
2. Sequences of the trp operon leader RNA resemble an operator.
3. The leader peptide acts by a mechanism that is similar to that of a repressor protein.
4.The leader peptide gene of the trp operon includes no Trp codons.
5. The leader peptide is an enzyme that catalyzes transcription attenuation.
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
What is the role of a substrate that controls a repressible operon?
a.
increase the production of inactive repressor proteins
b.
bind to the repressor protein and activate it
c.
bind to the repressor protein and deactivate it
d.
bind to the promoter region and decrease the affinity of RNA polymerase for the promoter
Chapter 15 Solutions
Campbell Biology in Focus (2nd Edition)
Ch. 15.1 - How does binding of the trp corepressor to its...Ch. 15.1 - Describe the binding of RNA polymerase,...Ch. 15.1 - WHAT IF? A certain mutation in E. coli changes the...Ch. 15.2 - Prob. 1CCCh. 15.2 - Compare the roles of general and specific...Ch. 15.2 - Prob. 3CCCh. 15.3 - WHAT IF? Suppose the mRNA being degraded in Figure...Ch. 15.3 - MAKE CONNECTIONS Inactivation of one of the X...Ch. 15.4 - Describe the role of complementary base pairing...Ch. 15.4 - WHAT IF? Study the microarray in Figure 15.17. If...
Ch. 15 - If a particular operon encodes enzymes for making...Ch. 15 - The functioning of enhancers is an example of A. a...Ch. 15 - Which of the following is an example of...Ch. 15 - Prob. 4TYUCh. 15 - Prob. 5TYUCh. 15 - Which of the following would not be true of cDNA...Ch. 15 - Prob. 7TYUCh. 15 - SCIENTIFIC INQUIRY Imagine you want to study one...Ch. 15 - FOCUS ON EVOLUTION DNA sequences can act as tape...Ch. 15 - FOCUS ON INTERACTIONS In a short essay (100150...Ch. 15 - Prob. 11TYU
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- Which of these BEST DESCRIBE tryptophan in the Trp Operon? A. Acts as a corepressor B. Acts as a coactivator C. Acts as an inducer D. Acts as an enhancerarrow_forwardStudy 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 promoterarrow_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_forward
- What would happen if the operator sequence of the trp operon contained a mutation that prevented the repressor protein from binding to the operator? (Explain what would happen in both the presence and absence of tryptophan)arrow_forwardHow does the lac operon regulate lactose digestion in bacteria?a. The repressor protein becomes a lactose-digesting enzyme onlywhen lactose is present.b. The repressor protein binds to the lac operon when lactose ispresent, blocking transcription.c. When lactose is present, it binds to the operator region of the lacoperon, activating transcription of the repressor protein gene.d. The repressor protein falls off the lac operon when lactose ispresent, and lactose-digesting genes are expressed.arrow_forwardIn the trp operon, if a mutation occurred in the gene for the repressor so that it could bind to the operator even in the absence of tryptophan____________. a) the inducer cannot bind trpO, so operon gene transcription occurs b) the active repressor cannot bind trpO, so operon gene transcription is attenuated c)the active repressor binds tpO, so operon gene transcription is always repressed d) the repressor binds the corepressor, and operon gene transcription occurs.arrow_forward
- In the lac operon, how would gene expression be affected if each one of the following segments was missing? A. lac operon promoter B. Operator site C. lacA genearrow_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_forwardIf lactose isn't present in the environment of an E. coli, what is the state of the lac operon? O a. It is "on" (high transcription) because will glucose will still be present, so the operon's products will be needed. O b. It is "on" (high transcription) because CAP will be bound to the promoter O c. It is "off" (no transcription) because RNA polymerase will be inactivated d. It is "off" (no transcription) and the repressor will be bound to the operatorarrow_forward
- How would each manipulation of the leader region of the trp mRNA affect transcription of the E. coli trp operon? 1. Increasing the distance (number of bases) between the leader peptide gene and sequence 2 would ___________________ transcriptional attenuation of the trp operon. (increase/decrease/not change) 2. Increasing the distance between sequences 2 and 3 would ____________________ transcriptional attenuation of the trp operon. (increase/decrease/not change) 3. Removing sequence 4 would ________________ transcriptional attenuation of the trp operon. (cause/not change/prevent) 4. Changing the two Trp codons in the leader peptide gene to His codons would cause transcriptional attenuation of the trp operon to ____________________. (lose its sensitivity to histidine/increase its sensitivity to tryptophan/lose its sensitivity to tryptophan) 5. Eliminating the ribosome‑binding site for the gene that encodes the leader peptide would cause transcriptional attenuation of the trp operon to…arrow_forwardWhich of the following environmental conditions would be MOST likely to result in transcription of the lac operon in an E. colicell? A. low levels of lactose and high levels of glucose B. high levels of lactose and high levels of cyclic AMP C. low levels of lactose and low levels of cyclic AMP D. high levels of lactose and high levels of glucosearrow_forwardWhat would occur if the repressor of an inducible operon weremutated so it could not bind the operator?(A) irreversible binding of the repressor to the promoter(B) reduced transcription of the operon’s genes(C) buildup of a substrate for the pathway controlled by theoperon(D) continuous transcription of the operon’s genesarrow_forward
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