Study Guide for Campbell Biology
11th Edition
ISBN: 9780134443775
Author: Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Jane B. Reece, Martha R. Taylor, Michael A. Pollock
Publisher: PEARSON
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Chapter 18, Problem 2TYK
Summary Introduction
Introduction: In genetics, an operon is the functional unit of a gene. Operon has a cluster of genes controlled by single promoter. Trp operon is a characteristic feature of many bacteria including Escherichia coli (E. coli). It is a gram-negative, rod-shaped bacteria living in the large intestine of higher vertebrates. In E. coli, tryp operon is used for the transcription of genes responsible for the production of an amino acid tryptophan. Trp operon is an example of the negative feedback mechanism, where the presence of increased levels of tryptophan switches off the trp operon.
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Students have asked these similar questions
In E. coli, induction in the lac operon and repression in the trp operon are both examples of
a. negative control by a repressor.
b. positive control by a repressor.
c. negative control by an activator.
d. positive control by a repressor.
Define the following in the context of operons:
a. positive control
b. give an example of an operon that is under positive control
c. negative control
d. give an example of an operon that is under negative control
e. repressor
f. give an example of a repressor molecule
g. activator
h. give an example of an activator
Which of the following statements about trp operon regulation is TRUE?
A. Low trp levels result in trp repressor binding.
O B. High trp levels result in transcriptional antitermination.
C. Low trp levels cause the ribosome to fall off at the trp codons in the upstream ORF.
O D. High trp levels cause the ribosome to fall off at the trp codons in the upstream ORF.
O E. Low trp levels result in transcriptional antitermination.
QUESTION 34
Consider the following partial diploid for the lac operon system.
lacl+ O+
lac Z+Y-A-
lacls O+
1.
2.
lac Z-Y+ A+
In this configuration, which of the following statements is TRUE?
A. With no lac present, ZYA will all be expressed.
B. with lac present none of the genes (ZYA) will be expressed.
O C. With no lac present, only YA will be expressed.
D. None of these answers is correct.
E. With no lac present, only Z will be expressed.
Chapter 18 Solutions
Study Guide for Campbell Biology
Ch. 18 - In the following diagram of the lac operon, an...Ch. 18 - a. Repressible enzymes usually function in _____...Ch. 18 - a. Give an example of highly methylated and...Ch. 18 - Label the components of the following diagram that...Ch. 18 - a. How is the process of alternate RNA splicing...Ch. 18 - a. Describe how miRNAs regulate gene expression....Ch. 18 - a. What is the difference between determination...Ch. 18 - What type of evidence established that Bicoid...Ch. 18 - a. List three genetic changes that can convert a...Ch. 18 - Complete the following concept map to help you...
Ch. 18 - Fill in the following table to help you organize...Ch. 18 - Prob. 3SYKCh. 18 - Prob. 1TYKCh. 18 - Prob. 2TYKCh. 18 - Prob. 3TYKCh. 18 - Prob. 4TYKCh. 18 - Prob. 5TYKCh. 18 - DNA methylation of cytosine bases a. initiates the...Ch. 18 - Which of the following is not true of enhancers?...Ch. 18 - Prob. 8TYKCh. 18 - A eukaryotic gene typically has all of the...Ch. 18 - Prob. 10TYKCh. 18 - Prob. 11TYKCh. 18 - Which of the following statements explains why a...Ch. 18 - Prob. 13TYKCh. 18 - Prob. 14TYKCh. 18 - Prob. 15TYKCh. 18 - Prob. 16TYKCh. 18 - What would be the fate of a Drosophila larva that...Ch. 18 - Prob. 18TYKCh. 18 - Prob. 19TYKCh. 18 - Prob. 20TYKCh. 18 - Prob. 21TYKCh. 18 - Prob. 22TYKCh. 18 - Prob. 23TYKCh. 18 - Which of the following would most likely account...
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- E. coli are grown on a medium containing lactose. Once glucose is added to the medium, the bacteria stop fermenting lactose. Which of the following BEST explains the observed effect? A. Cellular levels of cAMP are lowB.Glucose is bound to the promoter C. Repressor protein is bound to the operator D. Repressor protein is bound to the promoterarrow_forwardIn the trp operon, tryptophan is best characterized as being a: A. repressor B. inducer C. corepressor D. DNA-binding domainarrow_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
- 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 attenuationarrow_forwardControl 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_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_forward
- 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_forwardIf 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 proteinarrow_forwardWhat 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 promoterarrow_forward
- Theara operon is an inducible operon that controls the production of the sugar arabinose. When arabinose is present in a bacterium it binds to the protein AraC, and the complex binds to the initiator site to promote transcription. In this scenario, AraC is a(n) ________. a. activator b. inducer c. repressor d. operatorarrow_forwardWhen 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_forwardA mutation at the operator prevents the regulator protein from binding. What effect will this mutation have in the following types of operons? a. Regulator protein is a repressor of a repressible operon. b. Regulator protein is a repressor of an inducible operon.arrow_forward
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