Chapter 16 Regulation of Gene Expression in Prokaryotes1) Which term refers to a contiguous genetic complex that is under coordinate control? A) lysogenB) prototrophC) operonD) allostericE) attenuationAnswer: CSection: 16.22) Genetic regulation in eukaryotes can take place at a variety of levels from transcriptional to posttranslational. At which level is genetic regulation considered most likely in prokaryotes?A) transcriptionalB) cappingC) polyadenylation of the 3' end of the mRNAsD) intron processingE) exon processingAnswer: ASection: 16.1, 16.23) Which term would be applied to a regulatory condition that occurs when protein greatly reduces transcription when associated with a particular section of DNA?A) negative controlB) positive controlC) inhibitionD) activationE) stimulationAnswer: ASection: 16.14) Which term most appropriately refers to a regulatory protein in prokaryotes?A) translationB) RNA processingC) DNA binding proteinD) gyrase actionE) helicase activationAnswer: CSection: 16.1, 16.2, 16.41Copyright © 2012 Pearson Education, Inc.5) In the lactose operon, the product of structural gene lacZ is capable of ________.A) nonautonomous replicationB) forming lactose from two glucose moleculesC) replacing hexokinase in the early steps of glycolysisD) splitting the β-linkage of lactoseE) forming ATP from pyruvateAnswer: DSection: 16.26) Which of the following terms best characterizes catabolite repression associated with the lactose operon in E. coli?A) inducible systemB) repressible systemC) negative controlD) positive controlE) constitutiveAnswer: DSection: 16.37) When referring to attenuation in regulation of the tryptophan operon, it would be safe to say that when high levels of tryptophan are available to the organism, ________.A) the tryptophan operon is being transcribed at relatively high levelsB) translational termination is likelyC) transcriptional termination is likelyD) tryptophan is inactivating the repressor proteinE) ribosomes are stalling during translation of the attenuator regionAnswer: CSection: 16.68) Under the system of genetic control of the tryptophan operon, ________.A) when there are high levels of tryptophan in the medium, transcription of the trp operon occursat high levelsB) when there is no tryptophan in the medium, transcription of the trp operon occurs at high levelsC) when there are high levels of tryptophan in the medium, transcription of CAP (CRP) occurs athigh levelsD) when there are high levels of tryptophan in the medium, ribosomes "stall" and reduce the levels of tryptophan synthesizedE) no transcription occurs under any nutritional circumstance because negative controls inhibit transcriptionAnswer: BSection: 16.52Copyright © 2012 Pearson Education, Inc.9) This question relates to the regulation of enzymes involved in the synthesis of tryptophan in E. coli. If tryptophan is present in the medium and available to the bacterium, ________.A) the repressor is inactive and the tryptophan operon is "off"B) the repressor is inactive and the tryptophan operon is "on"C) the repressor is bound to the operator, thus blocking transcriptionD) the five structural genes associated with tryptophan synthesis are being transcribed at "induced" levelsE) positive control is occurringAnswer: CSection: 16.510) Certain mutations in the regulator gene of the lac system in E coli result in maximal synthesis of the Lac proteins (β-galactosidase, etc.) even in the absence of the inducer (lactose). Provide an explanation for this observation. Answer: Either there has been a mutation in the gene that produces the repressor or the operator is mutated so that it will not interact with the repressor.Section: 16.211) Describe in detail the actions of the regulatory proteins in inducible and repressible enzyme systems.Answer: Inducible system: The repressor is normally active, but the inducer inactivates the repressor. Repressible system: The repressor is normally inactive but is activated by the corepressor. Active repressors turn off transcription.Section: 16.1, 16.2, 16.312) Compare and contrast positive and negative control of gene expression in bacteria. Answer: Both forms of control result from an interaction of a molecule (usually considered to bea protein) with the genetic material (either RNA or DNA). Positive control results when the interaction stimulates transcription, whereas negative control occurs when the interaction inhibitstranscription.Section: 16.1, 16.2, 16.33Copyright © 2012 Pearson Education, Inc.13) (a) Describe, by labeled diagram, the structural components of the lactose operon in E. coli. (b) State the function of the lac regulator gene. (c) State the function of β-galactosidase in the lacsystem. (d) Show, by diagram, the manner in which lactose brings about transcription of the threestructural genes of the lac operon. (e) Explain why certain mutations in the regulator gene (I-) of the lac system result in maximal synthesis of β-galactosidase, permease, and transacetylase even in the absence of the inducer (lactose). Answer: (a) See appropriate diagrams in the Klug et al. text.(b) The regulator gene produces a repressor protein, which interacts with the operator to shut offtranscription. In the presence of lactose, the repressor protein does not interact with theoperator.(c) β-galactosidase cleaves the lactose sugar into its components glucose and galactose.(d) See appropriate diagrams in the Klug et al. text.(e) Such mutations provide modified proteins that are unable to associate with the operator toshut off transcription.Section: 16.214) The following table lists several genotypes associated with the lac operon in E. coli. For each, indicate with a "+" or a "-" whether β-galactosidase would be expected to be produced at induced levels. (Assume that glucose is not present in the medium.)β-galactosidase productionGenotype No Lactose On Lactose(a) I + O+ Z+/ F' I - O+ Z+(b) I - Oc Z+/ F'I - O+ Z-(c) I s Oc Z+/ F'I + O+ Z+(d) I - O+ Z+/ F' I - O+ Z+I+= wild-type repressorI-= mutant repressor (unable to bind to the operator)Is = mutant repressor (insensitive to lactose)O+= wild-type operatorOc= constitutive operator (insensitive to repressor)Answer: (a) - +(b) + +(c) + +(d) + +Section: 16.24Copyright © 2012 Pearson Education, Inc.15) The following table lists several genotypes associated with the lac operon in E. coli. For each, indicate with a "+" or a "-" whether active β-galactosidase would