Genetic Analysis: An Integrated Approach (2nd Edition)
2nd Edition
ISBN: 9780321948908
Author: Mark F. Sanders, John L. Bowman
Publisher: PEARSON
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Chapter 14, Problem 2P
Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:
a. operator
b. repressor
c. inducer
d. corepressor
e. promoter
f. positive regulation
g. allostery
h. negative regulation
i. attenuation
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When 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 protein
a. What is the function of operons in bacterial gene regulation?
b. Describe how a bacterial operon can be regulated by repressible proteins (such as the tryptophan operon). Include in your description both the “on” and “off” states of the operon. Key elements of your diagram should include: Co-repressor, Genes, mRNA, Operator, Operon, Promoter, Repressor, RNA polymerase.
Transcriptional repressor proteins (e.g., lac repressor), antisense RNA, and feedback inhibition are three different mechanisms that turn off the expression of genes and gene products. Which of these three mechanisms will be most effective in each of the following situations?
A. Shutting down the synthesis of a polypeptide
B. Shutting down the synthesis of mRNA
C. Shutting off the function of a protein For your answers to parts A–C that list more than one mechanism, which mechanism will be the fastest or the most efficient?
Chapter 14 Solutions
Genetic Analysis: An Integrated Approach (2nd Edition)
Ch. 14 - 12.1 Bacterial genomes frequently contain groups...Ch. 14 - Transcriptional regulation of operon gene...Ch. 14 - Why is it essential that bacterial cells be able...Ch. 14 - Identify similarities and differences between an...Ch. 14 - The transcription of -galactosidase and permease...Ch. 14 - 12.6 Is attenuation the product of an allosteric...Ch. 14 - The trpL region contains four repeated DNA...Ch. 14 - The CAP binding site in the lac promoter is the...Ch. 14 - What role does cAMP play in transcription of lac...Ch. 14 - How would a cap- mutation that produces an...
Ch. 14 - Explain the circumstances under which attenuation...Ch. 14 - Consider the transcription of genes of the...Ch. 14 - Describe the lytic and lysogenic life cycles of ...Ch. 14 - 12.14 Define antisense RNA, and describe how it...Ch. 14 - 12.15 Attenuation of trp operon transcription is...Ch. 14 - 12.16 In the lac operon, what are the likely...Ch. 14 - Identify which of the following lac operon haploid...Ch. 14 - Prob. 18PCh. 14 - 12.19 List possible genotypes for lac operon...Ch. 14 - Suppose each of the genotypes you listed in parts...Ch. 14 - 12.21 Four independent mutants (mutants A to D)...Ch. 14 - Suppose the lac operon partial diploid...Ch. 14 - Prob. 23PCh. 14 - 12.24 A repressible operon system, like the trp...Ch. 14 - 12.25 What is the likely effect of each of the...Ch. 14 - 12.26 Suppose that base substitution mutations...Ch. 14 - 12.27 Two different mutations affect. Mutant...Ch. 14 - How would mutations that inactivate each of the...Ch. 14 - The bacterial insertion sequence IS 10 uses...Ch. 14 - 12.34 Northern blot analysis is performed on...Ch. 14 - 12.37 The electrophoresis gel shown in part (a) is...Ch. 14 - Prob. 32PCh. 14 - The following hypothetical genotypes have genes A,...Ch. 14 - For an E. coli strain with the lac operongenotype...
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- The lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products. These mutations include: I - = produces a repressor protein that cannot bind to the operator region IS = produces a repressor protein that cannot be removed from the operator region OC = cannot bind a repressor protein Z - = produces a defective (non-functioning) β-galactosidase enzyme + = wild type Detail the functionality of the lac operon under the following genetic and cellular conditions. You do not need to consider the role of CAP in your analysis. Genes Repressed (yes/no) Constitutive (yes/no) I+ OC Z+ I+ O+ Z+ (Lactose present) I- O+ Z+arrow_forwardThe lac operon of E. coli controls the expression of genes that code for enzymes involved in lactose metabolism. Mutations to various regions of the lac operon have been discovered which affect both the control of gene expression and the function of the gene products. These mutations include: I - = produces a repressor protein that cannot bind to the operator region IS = produces a repressor protein that cannot be removed from the operator region OC = cannot bind a repressor protein Z - = produces a defective (non-functioning) β-galactosidase enzyme + = wild type Detail the functionality of the lac operon under the following genetic and cellular conditions. You do not need to consider the role of CAP in your analysis. Genes Repressed (yes/no) Constitutive (yes/no) IS O+ Z+ IS OC Z+arrow_forwardDescribe how the components of the trp operon system are affected by a mutation in trpC? Why is it that once enviornmental tryptophan is inserted into the cell, only the trp repressor is activated (turned on)?arrow_forward
- 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?arrow_forwardA 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 inhibitedarrow_forwardYou can determine the regulation of an unknown operon based on descriptions like those in the table below. For each row, choose whether the fact would suggest positive or negative or inducible or repressible regulation and indicate your answer with an X in the column. Only one X should appear in each row. In the presence of the signal, the structural genes are expressed. In the presence of the signal, the structural genes are not expressed. In the absence of the signal, the structural genes are expressed. In the absence of the signal, the structural genes are not expressed. The binding of the regulatory protein to the operon results in structural gene expression. The binding of the regulatory protein to the operon prevents structural gene expression. A mutation in the regulatory protein results in constitutive expression of the structural genes. A mutation in the regulatory protein results in no or low expression of the structural genes. Positive? Negative? Inducible? Repressible?arrow_forward
- For the following types of transcriptional control, indicate whether the protein produced by the regulator gene will be synthesized initially as an active repressor or as an inactive repressor. Q. Negative control in a repressible operonarrow_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_forwardConsider the following scenario: A bacteria cell is surrounded by lactose, but there is no glucose readily available. Will the lac operon be active (on) or inactive (off)? Explain in your own words. If it is active, describe the levels (low or high) of transcription, and any positive regulators assisting with this. If it is inactive, describe the negative regulators assisting with this, and how the operon could be turned on. Question 48 options: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_forwardFor the following types of transcriptional control, indicate whether the protein produced by the regulator gene will be synthesized initially as an active repressor or as an inactive repressor. Q. Negative control in an inducible operonarrow_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_forward
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