Concepts of Genetics (12th Edition)
12th Edition
ISBN: 9780134604718
Author: William S. Klug, Michael R. Cummings, Charlotte A. Spencer, Michael A. Palladino, Darrell Killian
Publisher: PEARSON
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Chapter 17, Problem 25ESP
Regulation of the lac operon in E. coli (see Chapter 16) and regulation of the GAL system in yeast are analogous in that they both serve to adapt cells to growth on different carbon sources. However, the transcriptional changes are accomplished very differently. Consider the conceptual similarities and differences as you address the following.
- (a) Compare and contrast the roles of the lac operon inducer in bacteria and Gal3p in eukaryotes in the regulation of their respective systems.
- (b) Compare and contrast the cis-regulatory elements of the lac operon and GAL gene system.
- (c) Compare and contrast how these two systems are negatively regulated such that they are downregulated in the presence of glucose.
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Predict the level of genetic activity of the lac operon as well as the status of the lac repressor and the CAP protein under the cellular conditions listed in the accompanying table. Lactose Glucose (a) - - (b) + - (c) - + (d) + +
In the topic about prokaryotic gene expression regulation, we learned about the LacI-, LacIS, and LacOc mutations. Based on your knowledge of allosteric regulation, invent and describe a hypothetical mutation that would produce constitutive expression of the Lac operon but is not a mutation that occurs in the Lac operator (that is, it must be a different mutation than a LacOc type mutation) and is not a mutation to the DNA binding domain of LacI (that is, it must also be a different mutation than a LacI- type mutation). Clearly mention where in the prokaryotic genome this mutation would occur, and explain the logic behind how that mutation would produce constitutive Lac operon expression.
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.
Chapter 17 Solutions
Concepts of Genetics (12th Edition)
Ch. 17 - Cancer cells often have abnormal patterns of...Ch. 17 - The hormone estrogen converts the estrogen...Ch. 17 - Each year in the United States, there are over...Ch. 17 - Prob. 2CSCh. 17 - Each year in the United States, there are over...Ch. 17 - HOW DO WE KNOW? In this chapter, we focused on how...Ch. 17 - CONCEPT QUESTION Review the Chapter Concepts list...Ch. 17 - What features of eukaryotes provide additional...Ch. 17 - Provide a definition of chromatin remodeling, and...Ch. 17 - Describe the organization of the interphase...
Ch. 17 - A number of experiments have demonstrated that...Ch. 17 - Provide a brief description of two different types...Ch. 17 - Present an overview of the manner in which...Ch. 17 - Prob. 9PDQCh. 17 - Explain how the addition of acetyl groups to...Ch. 17 - Distinguish between the cis-acting regulatory...Ch. 17 - Prob. 12PDQCh. 17 - Describe the manner in which activators and...Ch. 17 - Compare the control of gene regulation in...Ch. 17 - Many promoter regions contain CAAT boxes...Ch. 17 - Prob. 16PDQCh. 17 - Prob. 17PDQCh. 17 - Many transcriptional activators are proteins with...Ch. 17 - Prob. 19PDQCh. 17 - DNA supercoiling, which occurs when coiling...Ch. 17 - Prob. 21ESPCh. 17 - Prob. 22ESPCh. 17 - Because the degree of DNA methylation appears to...Ch. 17 - A particular type of anemia in humans, called...Ch. 17 - Regulation of the lac operon in E. coli (see...Ch. 17 - DNA methylation is commonly associated with a...Ch. 17 - During an examination of the genomic sequences...Ch. 17 - Prob. 28ESPCh. 17 - Although a single activator may bind many...Ch. 17 - Hereditary spherocytosis (HS) is a disorder...Ch. 17 - Transcription factors play key roles in the...
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- In the: Mutation of the regulatory region for a repressor protein in the lac operon. Explain: (a) What is the process affected? (b) What is the Effect on the process? (c) Does it affect prokaryotes, eukaryotes or both?arrow_forwardThe lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a single polycistronic mRNA. The new lac strain of Escherichia coli are as shown below: P+O+Z+Y+A+// P+O+Z+Y+A¯ (i) Illustrate how lactose induces the gene expression in lac 1 $// I-. (ii) Explain the function of the lacP and laco in the bacterial operon.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_forward
- For 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_forwardThe lac genotypes are as shown below: P+OcZ-Y+A+// P¯O+Z+Y+A+ (i) The lac operon consists of three structural genes, lacZ, lacY and lacA. Which structural genes are involved in lactose metabolism? Explain. (ii) Draw and explain how lactose repress the gene expression in lac IS/I- heterozygote. (iii) What is the function of the promoter in the bacterial operon?arrow_forwardExplain the process of attenuation in the trp operon under the following conditions: (i) No tryptophan (ii) High tryptophan levelsarrow_forward
- The lac operon consists of three structural genes, lacZ, lacY and lacA that are transcribed as a single polycistronic mRNA. You are given a new strain of Escherichia coli with the following lac operon genotype: p+0°Z•Y*A +// P*O*Z*Y+ A- (i) Explain how the lac I gene affects gene expression. (ii) Explain the function of the lacP in the bacterial operon. (iii) Which part of the lac operon is cis-dominant? Explain.arrow_forwardIn the lac operon (below), how will expression of the genes lacZ and lacy be effect by a mutation in the repressor protein (encoded by lach) that prevents it from binding the operator sequence (lacO) in the absence of lactose? Explain the answerarrow_forwardFor 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_forward
- 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 controlarrow_forwardThe lactose operon in E. coli comprises two structural genes and three regulatory components.a.State the name of each structural gene and describe its function: b.) State the name of each regulatory component and describe its functionarrow_forwardSuppose the tRNA synthetase responsible for attaching tryptophan to tRNA is muted in a bacterial strain with the result that the tRNA sythetase functions at twice the efficiency of the wild-type tRNA synthetase. Which of the following is most likely? a)the attenuation mechanism will not function normally and transcriptionof the trp operon will be less dependent upon intracellular tryptophan levels b)the attenuation mechanism will not function normally and transcriptionof the trp operon will be strongly dependent upon intracellular tryptophan levelsarrow_forward
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