Chapter 8 Microbiology

In negative control of transcription, how does the presence of an inducer affect transcription? A) The inducer prevents the repressor from binding to the operator. B) The inducer does not bind to the operator. C) The inducer causes the repressor to bind to the operator. D) The inducer binds to the operator.

A) The inducer prevents the repressor from binding to the operator.

What is the direct cause of catabolite repression? A) a cellular deficiency of cyclic AMP B) the synthesis of β-galactosidase C) binding of CAP to the DNA D) the presence of glucose and lactose in a growth medium

A) a cellular deficiency of cyclic AMP

The most frequent way in which regulatory RNA molecules exert their effects is by A) base pairing with other RNA molecules that have regions of complementary sequence. B) binding to a repressor and repressing enzyme transcription. C) signal transduction. D) acting as an inducer that then binds to an activator protein to allow transcription to proceed.

A) base pairing with other RNA molecules that have regions of complementary sequence.

In enzyme induction, a(n) ________ represses enzyme production. A) corepressor B) effector C) inducer D) repressor

A) corepressor

When considering the biological information flow, transcription is usually thought of as the A) first step. B) second step. C) third step. D) only step, because everything else flows from transcription.

A) first step.

Arginine in the culture medium A) represses the synthesis of the enzymes required for the production of arginine. B) has no effect on the enzymes required for the production of arginine. C) neutralizes the enzymes required for the production of arginine. D) enhances the synthesis of the enzymes required for the production of arginine.

A) represses the synthesis of the enzymes required for the production of arginine.

Cyclic AMP is synthesized from ATP by an enzyme called A) cAMP receptor protein (CRP) receptase. B) adenylate cyclase. C) catabolite activator protein (CAP) activase. D) RNA polymerase.

B) adenylate cyclase.

Regulation of an enzymeʹs activity occurs A) transcriptionally. B) posttranslationally. C) at any point on the enzymatic production pathway. D) translationally.

B) posttranslationally.

In the tryptophan operon, synthesis of the leader peptide results in A) initiation of transcription of the tryptophan structural genes. B) termination of transcription of the remainder of the trp operon. C) augmentation of transcription of the tryptophan structural genes. D) none of the above.

B) termination of transcription of the remainder of the trp operon.

When arginine is added to a culture growing exponentially in a medium without arginine, what occurs? A) The cell returns to the lag stage of growth to synthesize the proteins necessary for the metabolism of arginine. B) Growth continues, but the production of enzymes required for the synthesis of arginine increases. C) Growth continues, but the production of enzymes required for the synthesis of arginine ceases. D) All cellular growth ceases.

C) Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

What occurs when an inducer is added to an environment containing an organism with a metabolic pathway controlled by a repressor? A) The inducer does not combine with, but functions as a chaperone molecule for, the enzyme-substrate complex. B) The inducer combines with the substrate and blocks induction. C) The inducer combines with the repressor and inactivates the pathway. D) The inducer combines with the repressor and activates the pathway.

C) The inducer combines with the repressor and inactivates the pathway.

Regulatory proteins A) are influenced by small molecules. B) regulate transcription. C) bind to specific DNA sites. D) do all of the above.

C) bind to specific DNA sites.

Alternative sigma factors in the cell regulate the A) negative ionic response. B) electrical gradient response. C) heat shock response. D) RNA polymerase response

C) heat shock response.

The function of a kinase is A) glycosylation. B) response regulation. C) phosphorylation. D) methylation.

C) phosphorylation.

The promoters of positively controlled operons require activator proteins, because A) they are required to inactivate the repressor proteins. B) they are needed to bind to the allosteric site of RNA polymerase. C) the promoters have nucleotide sequences that bind RNA polymerase weakly, which are not close matches to the consensus sequence. D) RNA polymerase easily recognizes the consensus sequence.

C) the promoters have nucleotide sequences that bind RNA polymerase weakly, which are not close matches to the consensus sequence.

Enzyme repression and induction occur at the level of A) translation. B) posttranslation. C) transcription. D) pretranscription

C) transcription.

Endospore formation in Bacillus subtilis is triggered by adverse external conditions that are monitored by a five sensor kinase system whose mechanism resembles that of A) chemotaxis regulation. B) a stringent response. C) a heat shock response. D) a two-component regulatory system.

D) a two-component regulatory system.

Heat shock proteins perform which of the following functions? A) catalyze the correct folding of misfolded proteins B) remove denatured or irreversibly aggregated proteins C) prevent aggregation of newly synthesized proteins D) all of the above

D) all of the above

Which of the following is a major phases of the regulation of differentiation in prokaryotes? A) asymmetric development of two sister cells B) reciprocal communication between the two differentiating cells C) triggering of the response D) all of the above

D) all of the above

Which of the following is necessary for negative control of the tryptophan operon? A) operator B) leader sequence C) promoter D) all of the above

D) all of the above

Protein binding occurs at the ________ site of DNA. A) primary supercoil B) histone complex C) minor groove D) major groove

D) major groove

Attenuation occurs in the biosynthetic pathway for phenylalanine in Escherichia coli. Therefore, the leader sequence for this pathway will be rich in which of the following? A) histidine B) isoleucine C) threonine D) phenylalanine

D) phenylalanine

Histones are ________, so they combine strongly and relatively nonspecifically with ________ DNA. A) positively charged / neutral B) negatively charged / positively charged C) neutral / negatively charged D) positively charged / negatively charged

D) positively charged / negatively charged

Enzyme induction occurs A) when the organism is environmentally stressed. B) continuously. C) when the substrate is depleted. D) when the substrate is present.

D) when the substrate is present.