Biology
12th Edition
ISBN: 9781260494570
Author: Raven, Peter
Publisher: MCGRAW-HILL HIGHER EDUCATION
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Chapter 16, Problem 3U
Summary Introduction
In prokaryotic organisms, transcription is controlled by either positive or negative control. The positive and negative control is mediated by activators and repressors, respectively. Repressors are the molecules, which interfere with transcription, whereas activators induce or stimulate the transcription. Lac operon and trp operon are examples of prokaryotic regulation of transcription.
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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.
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
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
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?
Chapter 16 Solutions
Biology
Ch. 16.1 - Prob. 1LOCh. 16.1 - Prob. 2LOCh. 16.1 - Prob. 3LOCh. 16.2 - Explain how proteins can interact with base-pairs...Ch. 16.2 - Prob. 2LOCh. 16.3 - Prob. 1LOCh. 16.3 - Prob. 2LOCh. 16.3 - Explain control of gene expression in the trp...Ch. 16.4 - Prob. 1LOCh. 16.4 - Prob. 2LO
Ch. 16.4 - Prob. 3LOCh. 16.5 - Describe at least two kinds of epigenetic mark.Ch. 16.5 - Explain the function of chromatin-remodeling...Ch. 16.6 - Prob. 1LOCh. 16.6 - Prob. 2LOCh. 16.7 - Prob. 1LOCh. 16.7 - Prob. 2LOCh. 16 - Prob. 1DACh. 16 - What advantage might a bacterium gain by linking...Ch. 16 - Prob. 2IQCh. 16 - Prob. 3IQCh. 16 - In prokaryotes, control of gene expression usually...Ch. 16 - Prob. 2UCh. 16 - Prob. 3UCh. 16 - The lac operon is controlled by two main proteins....Ch. 16 - In eukaryotes, binding of RNA polymerase to a...Ch. 16 - In eukaryotes, the regulation of gene expression...Ch. 16 - In the trp operon, the repressor binds to DNA a....Ch. 16 - Prob. 1ACh. 16 - Specific transcription factors in eukaryotes...Ch. 16 - Repression in the trp operon and induction in the...Ch. 16 - Regulation by small RNAs and alternative splicing...Ch. 16 - Eukaryotic mRNAs differ from prokaryotic mRNAs in...Ch. 16 - In the cell cycle, cyclin proteins are produced in...Ch. 16 - A mechanism of control in E. coli not discussed in...Ch. 16 - You have isolated a series of mutants affecting...Ch. 16 - Examples of positive and negative control of...Ch. 16 - What forms of eukaryotic control of gene...Ch. 16 - The number and type of proteins found in a cell...
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- 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_forwardTheara 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_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
- 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.arrow_forwardIf CAP is bound to the Promoter of the Lac Operon and the repressor protein is not bound to the operator, which of the following is true: a.Glucose Levels are low & Lactose is absent b.Glucose is absent & Lactose is present c.cAMP is low & Lactose is Absent d.Glucose and Lactose are Present e.cAMP is low & Lactose is presentarrow_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_forward
- In the trp operon, tryptophan is best characterized as being a: A. repressor B. inducer C. corepressor D. DNA-binding domainarrow_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_forwardOperons can not be: a. Negatively regulated b. Positively regulated c. Constitutive d. Inducible e. Repressible f. coding for related structural proteins g. Expressed by use of RNA polymerase h. Dependent on a promoter for expressionarrow_forward
- If 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_forwardThe trp operon in E. coli is a negative repressible operon. This implies that... a. The trp operon makes use of an activator and can be turned "on" (i.e., is normally "off") b. The trp operon makes use of an activator and can be turned "off" (i.e., is normally "on) c. The trp operon makes use of a repressor and can be turned "on" (i.e., is normally "off") d. The trp operon makes use of a repressor and can be turned "off" (i.e., is normally "on") e. None of the abovearrow_forwardIn 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_forward
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