Deck 16: Gene Regulation in Bacteria

Question 1

The lac operon is under what type of control?

A) positive control
B) negative control
C) The gene would be expressed constitutively.
D) It depends on what the gene encodes.

Answer 1

B

Question 2

Regulation of gene expression may occur at which of the following levels?

A) transcription
B) translation
C) posttranslation
D) All of the answers are correct.

Answer 2

D

Question 3

A gene is inducible and under negative control.Which of the following pairs will allow expression of this gene?

A) activator + repressor
B) activator + inhibitor
C) repressor + inducer
D) repressor + corepressor

Answer 3

C

Question 4

Enzymes involved in metabolism are most likely regulated via ________.

A) feedback inhibition
B) acetylation
C) methylation
D) None of the answers are correct.

Question 5

How many promoters are in an operon?

A) 1
B) 2
C) 3
D) It depends on how many genes there are in the operon.

Question 6

In Jacob,Monod,and Pardee's experiment,how many functional copies of lacI were there in the merozygote?

A) 0
B) 1
C) 2
D) 3

Question 7

If CAP could not bind to its CAP site,then what would be the result? Assume lactose is present in each scenario.

A) Transcription would be difficult to repress in the presence of glucose.
B) Transcription would be difficult to activate in the presence of glucose.
C) Transcription would be difficult to activate in the absence of glucose.
D) Transcription would be difficult to repress in the absence of glucose.

Question 8

Allosteric regulation is accomplished by

A) a small molecule that fits into an enzyme's active site.
B) a large protein that blocks an enzyme's active site.
C) a small molecule that fits into a site on the enzyme that is not the active site.
D) a small molecule that covalently modifies a site on the enzyme that is not the active site.

Question 9

What would be the result if the U-rich sequence after the fourth stem loop in the trp operon was replaced by a UG-rich sequence?

A) Attenuation would occur if tryptophan was high.
B) Attenuation would occur if tryptophan is low.
C) Attenuation would not occur if tryptophan was high.
D) None of the answers are correct.

Question 10

CAP affects which operon(s)?

A) the lac operon
B) the trp operon
C) both the lac and the trp operon
D) neither the lac nor the trp operon

Question 11

Which of the following is not an example of translational regulation in prokaryotes?

A) sterically blocking the ribosome
B) phosphorylation of an enzyme
C) incorporation of antisense RNA
D) altering the structure of the mRNA

Question 12

In the Jacob Monod merozygote experiment,what was indicated by the presence of a yellow color when b-ONPG was added?

A) Expression of the lac operon is constitutive whether lacI is functional or not.
B) Beta-galactosidase was present.
C) The lac operon was completely turned off.
D) The researcher added too much b-ONPG.

Question 13

A riboswitch is an RNA molecule that can exist in two different conformations.Conversion from one to another is due to the binding of a small molecule to the riboswitch.

Question 14

Which of the following is found in an operon?

A) promoter
B) terminator
C) two or more genes
D) operator
E) All of the answers are correct.

Question 15

In the lac operon,the operator is an example of a trans-effect genetic regulation.

Question 16

If a bacterium is placed in an environment that contains both glucose and lactose,the regulation of the lac operon will allow which nutrient to be processed first?

A) glucose
B) lactose
C) Both will be processed equally.
D) Neither will be processed in this environment.

Question 17

Which of the following is not associated with positive transcriptional regulation?

A) activators
B) inducers
C) corepressors
D) All of the answers are involved in positive regulation.

Question 18

What stem-loop conformations favor attenuation in the trp operon?

A) 1-2
B) 1-2 and 2-3
C) 2-3
D) 1-2 and 3-4

Question 19

Which of the following encode polycistronic mRNA?

A) lac operon
B) ara operon
C) trp operon
D) All of the answers are correct.

Question 20

What is the gene responsible for attenuation in the trp operon?

A) trpL
B) trpR
C) trpD
D) trpC

Question 21

Antisense RNA does which of the following?

A) inhibits the formation of the open complex in transcription
B) occupies the A and P sites of the ribosome
C) binds to the mRNA and prevents translation
D) prevents the correct folding of a newly formed peptide

Question 22

The term enzyme adaptation is used to describe an enzyme that appears in a living cell following exposure to a specific substrate.

Question 23

Translational regulatory proteins recognize specific areas of what molecule?

A) tRNA
B) Ribosome
C) rRNA
D) mRNA
E) None of the answers are correct.

Question 24

The regulation of protein function,not gene expression is called ________ regulation.

A) posttranslational
B) transcriptional
C) translational
D) posttranscriptional

Question 25

Constitutive genes are those that have constant levels of expression.

Question 26

Riboswitches have been shown to have regulation of ________.

A) transcription and translation
B) only transcription
C) only translation
D) only RNA splicing

Question 27

Operons that code for anabolic enzyme systems are typically regulated by inducers.

Question 28

Negative transcriptional regulation is conducted by activator proteins.

Question 29

Operons that code for catabolic enzyme systems are typically regulated by repressors.

Question 30

In the trp operon,tryptophan is a corepressor.

Question 31

In the E.coli riboswitch,mRNA gets translated when TPP is low.

Question 32

In the lac operon,the operator site is recognized by an activator protein.

Question 33

The form of regulation that involves a physical change in the shape of an enzyme is called allosteric regulation.

Question 34

Because it stabilizes mRNA, antisense RNA enhances translation.

Question 35

Repressor proteins are responsible for negative transcriptional regulation.

Question 36

cAMP is a small effector molecule.

Question 37

Coupled transcription and translation occur under conditions in which the tryptophan concentration is very low.