Campbell s Biology 9e Reece et al Chapter 18 Regulation of Gene Expression Chapter 18 includes new questions for every concept number some of these questions cover new topics whereas others build on existing questions Several new questions introduce scenarios and art thus encouraging a higher level of thinking from students Multiple Choice Questions 1 The role of a metabolite that controls a repressible operon is to A bind to the promoter region and decrease the affinity of RNA polymerase for the promoter B bind to the operator region and block the attachment of RNA polymerase to the promoter C increase the production of inactive repressor proteins D bind to the repressor protein and inactivate it E bind to the repressor protein and activate it Answer E Topic Concept 18 1 Skill Knowledge Comprehension 2 The tryptophan operon is a repressible operon that is A permanently turned on B turned on only when tryptophan is present in the growth medium C turned off only when glucose is present in the growth medium D turned on only when glucose is present in the growth medium E turned off whenever tryptophan is added to the growth medium Answer E Topic Concept 18 1 Skill Knowledge Comprehension 3 Which of the following is a protein produced by a regulatory gene A operon B inducer C promoter D repressor E corepressor Answer D Topic Concept 18 1 Skill Knowledge Comprehension 4 A lack of which molecule would result in the cell s inability to turn off genes A operon B inducer C promoter D ubiquitin E corepressor Answer E Topic Concept 18 1 Skill Knowledge Comprehension 1 Copyright 2011 Pearson Education Inc 5 Which of the following when taken up by the cell binds to the repressor so that the repressor no longer binds to the operator A ubiquitin B inducer C promoter D repressor E corepressor Answer B Topic Concept 18 1 Skill Knowledge Comprehension 6 Most repressor proteins are allosteric Which of the following binds with the repressor to alter its conformation A inducer B promoter C RNA polymerase D transcription factor E cAMP Answer A Topic Concept 18 1 Skill Knowledge Comprehension 7 A mutation that inactivates the regulatory gene of a repressible operon in an E coli cell would result in A continuous transcription of the structural gene controlled by that regulator B complete inhibition of transcription of the structural gene controlled by that regulator C irreversible binding of the repressor to the operator D inactivation of RNA polymerase by alteration of its active site E continuous translation of the mRNA because of alteration of its structure Answer A Topic Concept 18 1 Skill Application Analysis 8 The lactose operon is likely to be transcribed when A there is more glucose in the cell than lactose B the cyclic AMP levels are low C there is glucose but no lactose in the cell D the cyclic AMP and lactose levels are both high within the cell E the cAMP level is high and the lactose level is low Answer D Topic Concept 18 1 Skill Knowledge Comprehension 2 Copyright 2011 Pearson Education Inc 9 Transcription of the structural genes in an inducible operon A occurs continuously in the cell B starts when the pathway s substrate is present C starts when the pathway s product is present D stops when the pathway s product is present E does not result in the production of enzymes Answer B Topic Concept 18 1 Skill Knowledge Comprehension 10 For a repressible operon to be transcribed which of the following must occur A A corepressor must be present B RNA polymerase and the active repressor must be present C RNA polymerase must bind to the promoter and the repressor must be inactive D RNA polymerase cannot be present and the repressor must be inactive E RNA polymerase must not occupy the promoter and the repressor must be inactive Answer C Topic Concept 18 1 Skill Knowledge Comprehension 11 Allolactose an isomer of lactose is formed in small amounts from lactose An E coli cell is presented for the first time with the sugar lactose containing allolactose as a potential food source Which of the following occurs when the lactose enters the cell A The repressor protein attaches to the regulator B Allolactose binds to the repressor protein C Allolactose binds to the regulator gene D The repressor protein and allolactose bind to RNA polymerase E RNA polymerase attaches to the regulator Answer B Topic Concept 18 1 Skill Knowledge Comprehension 12 Altering patterns of gene expression in prokaryotes would most likely serve the organism s survival in which of the following ways A organizing gene expression so that genes are expressed in a given order B allowing each gene to be expressed an equal number of times C allowing the organism to adjust to changes in environmental conditions D allowing young organisms to respond differently from more mature organisms E allowing environmental changes to alter the prokaryote s genome Answer C Topic Concept 18 1 Skill Synthesis Evaluation 3 Copyright 2011 Pearson Education Inc 13 In response to chemical signals prokaryotes can do which of the following A turn off translation of their mRNA B alter the level of production of various enzymes C increase the number and responsiveness of their ribosomes D inactivate their mRNA molecules E alter the sequence of amino acids in certain proteins Answer B Topic Concept 18 1 Skill Knowledge Comprehension 14 If glucose is available in the environment of E coli the cell responds with a very low concentration of cAMP When the cAMP increases in concentration it binds to CAP Which of the following would you expect to be a measurable effect A decreased concentration of the lac enzymes B increased concentration of the trp enzymes C decreased binding of the RNA polymerase to sugar metabolism related promoters D decreased concentration of alternative sugars in the cell E increased concentrations of sugars such as arabinose in the cell Answer E Topic Concept 18 1 Skill Synthesis Evaluation 15 In positive control of several sugar metabolism related operons the catabolite activator protein CAP binds to DNA to stimulate transcription What causes an increase in CAP A increase in glucose and increase in cAMP B decrease in glucose and increase in cAMP C increase in glucose and decrease in cAMP D decrease in glucose and increase in repressor E decrease in glucose and decrease in repressor Answer B Topic Concept 18 1 Skill Knowledge Comprehension 16 There is a mutation in the repressor that results in a molecule known as a super repressor because it