Campbell Biology Chapter 18 Exam with correct answers - Graded A+

Campbell Biology Chapter 18 Exam with correct answers - Graded A+ Why is the lac operon said to be an inducible operon? When allolactose is present, it induces repression of gene expression. When activated, the lac operon induces repression of gene expression. When allolactose is present, it induces the activation of the lac repressor. When activated, the lac operon induces the production of lactose-digesting enzymes. When allolactose is present, it induces the inactivation of the lac repressor. - Answer- When allolactose is present, it induces the inactivation of the lac repressor. The role of a metabolite that controls a repressible operon is to increase the production of inactive repressor proteins. bind to the repressor protein and activate it. bind to the repressor protein and inactivate it. bind to the operator region and block the attachment of RNA polymerase to the promoter. bind to the promoter region and decrease the affinity of RNA polymerase for the promoter. - Answer- bind to the repressor protein and activate it. The tryptophan operon is a repressible operon that is turned on only when glucose is present in the growth medium. turned off only when glucose is present in the growth medium. permanently turned on. turned off whenever tryptophan is added to the growth medium. turned on only when tryptophan is present in the growth medium. - Answer- turned off whenever tryptophan is added to the growth medium. Which of the following is a protein produced by a regulatory gene? operon corepressor promoter inducer repressor - Answer- repressor A lack of which molecule would result in the cell's inability to "turn off" genes? corepressor operon ubiquitin inducer promoter - Answer- corepressor Which of the following, when taken up by the cell, binds to the repressor so that the repressor no longer binds to the operator? ubiquitin promoter corepressor repressor inducer - Answer- inducer Most repressor proteins are allosteric. Which of the following binds with the repressor to alter its conformation? transcription factor cAMP RNA polymerase promoter inducer - Answer- inducer A mutation that inactivates the regulatory gene of a repressible operon in an E. coli cell would result in continuous transcription of the structural gene controlled by that regulator. inactivation of RNA polymerase by alteration of its active site. complete inhibition of transcription of the structural gene controlled by that regulator. irreversible binding of the repressor to the operator. continuous translation of the mRNA because of alteration of its structure. - Answer- continuous transcription of the structural gene controlled by that regulator The lactose operon is likely to be transcribed when the cyclic AMP levels are low. the cyclic AMP and lactose levels are both high within the cell. there is glucose but no lactose in the cell. there is more glucose in the cell than lactose. the cAMP level is high and the lactose level is low. - Answer- the cyclic AMP and lactose levels are both high within the cell Transcription of the structural genes in an inducible operon occurs continuously in the cell. stops when the pathway's product is present. starts when the pathway's product is present. starts when the pathway's substrate is present. does not result in the production of enzymes. - Answer- starts when the pathway's substrate is present For a repressible operon to be transcribed, which of the following must occur? RNA polymerase must bind to the promoter, and the repressor must be inactive. RNA polymerase and the active repressor must be present. RNA polymerase cannot be present, and the repressor must be inactive. A corepressor must be present. RNA polymerase must not occupy the promoter, and the repressor must be inactive. - Answer- RNA polymerase must bind to the promoter, and the repressor must be inactive 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? RNA polymerase attaches to the regulator. The repressor protein attaches to the regulator. Allolactose binds to the repressor protein. Allolactose binds to the regulator gene. The repressor protein and allolactose bind to RNA polymerase. - Answer- Allolactose binds to the repressor protein Altering patterns of gene expression in prokaryotes would most likely serve the organism's survival in which of the following ways? allowing young organisms to respond differently from more mature organisms allowing the organism to adjust to changes in environmental conditions allowing environmental changes to alter the prokaryote's genome allowing each gene to be expressed an equal number of times organizing gene expression so that genes are expressed in a given order - Answer- allowing the organism to adjust to changes in environmental conditions