Biology, 8e (Campbell) Chapter 18 Regulation of Gene Expression Multiple-Choice Questions 1) What does the operon model attempt to explain? A) the coordinated control of gene expression in bacteria B) bacterial resistance to antibiotics C) how genes move between homologous regions of DNA D) the mechanism of viral attachment to a host cell E) horizontal transmission of plant viruses 2) 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. 3) 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. 4) This protein is produced by a regulatory gene: A) operon B) inducer C) promoter D) repressor E) corepressor 5) A mutation in this section of DNA could influence the binding of RNA polymerase to the DNA: A) operon B) inducer C) promoter D) repressor E) corepressor 6) A lack of this nonprotein molecule would result in the inability of the cell to "turn off" genes: A) operon B) inducer C) promoter D) repressor E) corepressor 7) When this is taken up by the cell, it binds to the repressor so that the repressor no longer binds to the operator: A) operon B) inducer 1
C) promoter D) repressor E) corepressor 8) 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. 9) 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. 10) 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.
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