Chapter 6

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

A- Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

When is the repressor protein transcribed? A- It is always transcribed. B- Only in the presence of tryptophan C- Only in the absence of tryptophan

A- It is always transcribed.

Which of the following is an example of negative control using an inducible system? A- The lac operon in E. coli is turned off unless lactose is present. A repressor binds to the operator and prevents RNA polymerase from binding to the promoter. When allolactose (closely related to lactose) is present, it binds to the repressor and prevents the repressor from binding. In this way, the presence of lactose allows the operon to be turned on to express the genes need to use lactose. B- Glucose inhibits the synthesis of cyclic AMP and stimulates cyclic AMP transport out of the cell. The lower cyclic AMP levels prevent CRP from binding DNA, and RNA polymerase cannot bind to the promoters of operons subject to catabolite repression. C- The trp operon in E. coli is turned on by default. When there are sufficient amounts of tryptophan, a repressor can bind to the operator to turn off the operon. Additionally, when there are sufficient amounts of tryptophan, attenuation occurs and the operon is turned off. D- The maltose operons in E. coli are turned off by default. When maltose is present, it binds to the maltose activator protein. The maltose activator protein can then bind to the activator binding site to allow the genes of the operons to be expressed. (There are multiple operons affected by the maltose activator protein).

A- The lac operon in E. coli is turned off unless lactose is present. A repressor binds to the operator and prevents RNA polymerase from binding to the promoter. When allolactose (closely related to lactose) is present, it binds to the repressor and prevents the repressor from binding. In this way, the presence of lactose allows the operon to be turned on to express the genes need to use lactose.

What is the overall function of the trp operon? A- To ensure that the cell has a supply of tryptophan at all times B- To control the production of repressor proteins C- To block RNA polymerase from the structural genes D- To always make sure the operator is being bound to repressor proteins

A- To ensure that the cell has a supply of tryptophan at all times

Why is the tryptophan operon turned off in the presence of tryptophan? A- Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription. B- Tryptophan can be used over and over again in the cell. C- Tryptophan is not an important amino acid for cells.

A- Tryptophan binds to and activates the repressor proteins; the repressor proteins, in turn, bind to the operator, preventing transcription.

Chemotaxis in bacteria occurs through the use of A- a modified two-component system. B- quorum sensing. C- autoinduction. D- adaptation.

A- a modified two-component system.

Cyclic AMP is synthesized from ATP by an enzyme called ________ which is involved in ________. A- adenylate cyclase / catabolite repression B- cAMP receptor protein (CRP) synthase / catabolite repression C- adenylate cyclase / transcriptional activation D- cAMP receptor protein (CRP) synthase / transcriptional activation

A- adenylate cyclase / catabolite repression

Global regulatory systems include all of the following EXCEPT A- amino acid synthesis. B- anaerobic respiration. C- heat shock response. D- transformation.

A- amino acid synthesis.

Attenuation is a type of regulation that can control A- translational activity exclusively. B- transcriptional activity exclusively. C- allosteric enzyme activity. D- both transcriptional and translational activity.

B- transcriptional activity exclusively.

Bacteria can regulate gene expression due to changes in the environment. How are these changes communicated to the cell? A- A sensor kinase on the cell membrane recognizes the change and transfers the information to the repressor or inducer molecule, which then binds to DNA. B- A sensor kinase on the cell membrane recognizes the change and transfers the information to a response regulator in the cytoplasm. C- A sensor kinase in the cytoplasm recognizes a change and transfers the information to a response regulator on the cell membrane. D- A response regulator on the cell membrane recognizes the change and transfers the information to a sensor kinase in the cytoplasm.

B- A sensor kinase on the cell membrane recognizes the change and transfers the information to a response regulator in the cytoplasm.

What is the inducer molecule in the lac operon? A- Galactose B- Allolactose C- Lactose D- Glucose E- Repressor proteins

B- Allolactose

In the lac operon, which of the following conditions would allow the structural genes to be transcribed? A- Lactose and glucose are present. B- Lactose is present and glucose is absent. C- Lactose and glucose are absent. D- Glucose is present and lactose is absent.

B- Lactose is present and glucose is absent.

When the nontemplate strand of a gene is transcribed into RNA, what is likely to result? A- A global regulator will identify this as a stress, respond by inducing ribonuclease production, and it will be degraded. B- The complementary mRNA transcribed from the template strand will bind to it and halt its translation. C- A complementary sRNA will bind to it and form a functional ribozyme with secondary structure. D- It will complementarily bind to the gene sequence, form a hairpin loop, and transcriptionally repress the gene.

B- The complementary mRNA transcribed from the template strand will bind to it and halt its translation.

What is the basic function of the lac operon? A- To code for enzymes involved in synthesizing lactose. B- To code for enzymes involved in catabolizing lactose. C- To produce glucose when none is available D- To produce lactose when none is present

B- To code for enzymes involved in catabolizing lactose.

How is the activity of a riboswitch controlled? A- sigma factor binding alters its structure B- metabolite binding can change its structure C- by other riboswitches D- small RNA complementary binding disrupts its function

B- metabolite binding can change its structure

When the cell is not in the presence of lactose, A- the repressor proteins are inactivated. B- the repressor proteins bind to the operator. C- transcription of the structural genes occurs. D- no transcription of the regulatory genes occurs.

B- the repressor proteins bind to the operator.

The major site of protein binding in DNA is the major groove. Why is this a good site for binding? A- The major groove has a more heavily methylated base composition, which aids in the binding of proteins. B- Because the minor groove is wider, it is more accessible to binding proteins. C- Because the major groove is wider, it is more accessible to binding proteins. D- The major groove has lower frequencies of inverted repeats; this lower frequency of inverted repeats makes binding easier.

C- Because the major groove is wider, it is more accessible to binding proteins.

Mechanisms for controlling enzyme activity include all of the following EXCEPT A- degradation of the enzyme. B- feedback inhibition. C- addition of short sections of new amino acid sequence. D- covalent modification of the enzyme.

C- addition of short sections of new amino acid sequence.

Which of the following do NOT bind to the promoter sequence during regulation? A- inducers B- activators C- repressors D- None of these bind directly to the promoter sequence.

D- None of these bind directly to the promoter sequence.

When the cell is NOT in the presence of tryptophan, A- the repressor proteins are active. B- the repressor proteins bind to the operator. C- structural genes are not transcribed. D- RNA polymerase can transcribe mRNA.

D- RNA polymerase can transcribe mRNA.

With which genetic region does the repressor protein interact? A- lacZ B- The regulatory gene C- The promoter region D- The operator region E- lacY

D- The operator region

According to the animation, to what genetic element does the RNA polymerase bind? A- The repressor protein B- The operator C- The repressor mRNA D- The promoter

D- The promoter

When more than one operon is under the control of a single regulatory protein, the operons are collectively called a(n) A- operator. B- riboswitch. C- autoinducer. D- regulon.

D- regulon.

According to the animation, how do the repressor proteins block the transcription of the structural genes? A- It binds to the repressor gene when deactivated. B- It binds to the promoter when activated. C- It binds to the repressor when deactivated. D- It binds to the promoter when deactivated. E- It binds to the repressor gene when activated . F- It binds to the operator when activated.

F- It binds to the operator when activated.

Small molecules usually act directly (rather than indirectly) in regulating transcription. True False

False

Proteins required at approximately the same level throughout a cells growth cycle are often not subject to regulatory mechanisms and are constitutively synthesized. True False

True