Deck 14: Regulation of Gene Expression in Bacteria and Bacteriophage

Question 1

In negative control,what molecule would you expect to find bound to the operator if there is no transcription?

A)activator
B)repressor
C)inducer
D)corepressor
E)RNA polymerase

Answer 1

B

Question 2

During the attenuation of the trp operon,which stem loop leads to polycistronic mRNA synthesis during tryptophan starvation?

A)1-3 (antitermination)stem loop
B)3-4 (termination)stem loop
C)1-2 (pause)stem loop
D)2-3 (antitermination)stem loop
E)2-4 (termination)stem loop

Answer 2

D

Question 3

Which mutants are noninducible?

A)lacIˢ
B)lacI⁻
C)lacI⁺
D)lacOᶜ
E)lacO⁺

Answer 3

A

Question 4

Which of these haploid strains produce permease but do not produce β-galactosidase?

A)I⁻ ᴾ⁺ ᴼ⁺ ᶻ⁺ ʸ⁺
B)I⁺ ᴾ⁺ ᴼ⁺ ᶻ⁻ʸ⁺
C)I⁻ ᴾ⁺ ᴼ⁺ ᶻ⁻ʸ⁻
D)I⁺ ᴾ⁺ ᴼ⁻ ᶻ⁺ ʸ⁺
E)I⁻ ᴾ⁺ ᴼ⁺ ᶻ⁺ ʸ⁻

Question 5

Which enzyme is responsible for integration of a temperate phage into a host genome?

A)β-galactosidase
B)transposase
C)integrase
D)transacetylase
E)permease

Question 6

The presence of which combination of molecules would lead to active transcription of an operon?

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

Question 7

A bacterium is unable to transport lactose into the cell to be broken down.Which gene is likely mutated in this bacterium?

A)lacZ
B)lacY
C)lacI
D)lacP
E)lacO

Question 8

In the presence of glucose,where is the lac repressor bound?

A)lacZ
B)lacO
C)lacP
D)lacI
E)The lac repressor is not bound to the operon.

Question 9

Which region of the lambda phage genome enables the linear chromosome to circularize when it enters a host cell?

A)cohesive (cos)site
B)IS10
C)early operators
D)integrase (int)gene
E)excisionase (xis)gene

Question 10

Which of these haploid strains produce β-galactosidase constitutively but do not produce permease?

A)I⁻ ᴾ⁺ ᴼ⁺ ᶻ⁺ ʸ⁺
B)I⁺ ᴾ⁺ ᴼ⁺ ᶻ⁻ ʸ⁻
C)I⁻ ᴾ⁺ ᴼ⁺ ᶻ⁻ʸ⁺
D)I⁺ ᴾ⁺ ᴼ⁻ ᶻ⁺ ʸ⁺
E)I⁻ ᴾ⁺ ᴼ⁺ ᶻ⁺ ʸ⁻

Question 11

Which structural gene of the lac operon can be mutated without affecting the cell's ability to break down lactose?

A)lacZ
B)lacY
C)lacA
D)lacP
E)lacO

Question 12

Which sigma factor,encoded by the rpoH gene,is active at high temperatures?

A)σ⁷⁰
B)σ³²
C)σ⁴⁵
D)σ³⁷
E)σ⁵⁰

Question 13

Which of the following are constitutive mutants of the lac operon?

A)lacZ and lacP
B)lacZ and lacI
C)lacO and lacI
D)lacO and lacZ
E)lacI and lacY

Question 14

In the lac operon,what acts as the inducer?

A)glucose
B)permease
C)allolactose
D)β-galactosidase
E)transacetylase

Question 15

If you wanted to prevent a cell from entering the lysogenic pathway,which gene controlled by PRM would you target?

A)cro
B)Q
C)cI
D)cII
E)O

Question 16

In λ phage,which protein,the product of the cI gene,blocks the transcription required to initiate the lytic cycle?

A)cro
B)repressor
C)enhancer
D)integrase
E)operator

Question 17

In the absence of tryptophan,

A)the inactive repressor cannot bind trpO,so operon gene transcription occurs.
B)the active repressor binds trpP,so operon gene transcription is repressed.
C)the inducer cannot bind trpO,so operon gene transcription occurs.
D)the active repressor cannot bind trpO,so operon gene transcription is attenuated.
E)the repressor binds the corepressor,and operon gene transcription occurs.

Question 18

Which region of the lac operon would you target if you want to disrupt the -10 and -35 consensus sequences?

A)lacZ
B)lacY
C)lacI
D)lacP
E)lacO

Question 19

The enzyme β-galactosidase catalyzes what reaction?

A)allolactose → glucose + lactose
B)lactose → glucose + fructose
C)lactose → galactose + glucose
D)glucose → galactose + lactose
E)galactose → glucose + lactose

Question 20

You want to design a repressor protein mutant.Which protein domain is the best target for preventing binding of the corepressor?

A)DNA-binding domain
B)allosteric domain
C)promoter domain
D)helix-turn-helix domain
E)activator binding site

Question 21

Bacteria grown at 45°C initiate expression of which two types of proteins?

Question 22

Which molecule functions as the corepressor in the trp operon?

Question 23

Which part of the lac operon produces a regulatory protein that is trans-acting?

Question 24

Catabolite repression refers to the repression of the lac operon in the presence of which catabolite?

Question 25

What are the two active sites or "domains" on a repressor protein?

Question 26

Antisense control of translation involves the regulation of which enzyme produced by bacterial insertion sequence IS10?

Question 27

Binding of which complex increases the ability of RNA polymerase to transcribe the lac operon?

Question 28

What protein cleaves the λ repressor monomers to inactivate the repressor protein,and is activated by DNA-damaging agents?

Question 29

Which part of the lac operon is cis-dominant?

Question 30

In the trp operon,where is the attenuator region located?

Question 31

The genetic switch controlling whether a bacterium enters the lytic or lysogenic cycle relies on the binding of which two proteins?

Question 32

Which proteins facilitate RNA polymerase binding at promoters?

Question 33

Which protein in the arabinose operon is responsible for both positive and negative regulation of transcription?

Question 34

What is the process by which a bacterium switches from a lysogenic to lytic cycle?

Question 35

What are the three possible alternative stem loops that can form in mRNA?

Question 36

Which enzyme is the product of the lacZ gene?

Question 37

Mutations of trpL decrease the efficiency of transcriptional regulation by disrupting the formation of which stem-loop structure?

Question 38

If a corepressor is inhibited,what effect would you expect to see in the operon?

Question 39

Regulation of transcription of bacterial genes takes place at which two levels?

Question 40

In the absence of both glucose and lactose,the presence of which molecule is capable of inducing basal transcription?

Question 41

Describe the difference between inducible and repressible operons.How does attenuation differ from inducible or repressible operons?
Which of the two inducible operons you've studied would be active if a cell has the following food sources?
a. only lactose
b. only glucose
c. only arabinose
d. lactose and glucose
e. glucose and arabinose
f. lactose and arabinose

Question 42

How does the arabinose (ara)operon accomplish both positive and negative transcriptional regulation? Describe the unique DNA structure that forms during one of these mechanisms,and include a diagram to illustrate the structure of the operon in both the presence and absence of arabinose.

Question 43

Bacterial translation is inhibited by ________ RNA,which is complementary to a portion of a specific mRNA.

Question 44

Most of the regulation of gene expression in bacteria occurs at the ________ level.

Question 45

DNA-binding proteins exert control by binding DNA at specific sequences.Describe how DNA and protein interact at the molecular level.Are proteins able to identify specific DNA sequences,or do they bind to all regions with equal frequency? What motifs are commonly found in DNA-binding proteins?

Question 46

Expression of a(n)________ alters gene transcription in E.coli by activating transcription of specialized heat stress response genes.

Question 47

What is the purpose of the lac operon,and under what circumstances is it activated? Describe the structure of the lac operon,including the repressor protein,structural genes,and regulatory regions of the operon.What is the role of catabolite repression in the lac operon?

Question 48

In λ phage,entry into the ________ cycle requires transcription of late genes.

Question 49

Changing conformation at the active site as a result of binding a substance at a different site is known as ________.

Question 50

What is the role of cis-acting and trans-acting factors in transcription? Explain how these factors play a role in the lac operon,and discuss how complementation can be used to identify where the mutations have occurred (structural genes versus regulatory regions).Which type of mutations can be complemented by a second gene with normal function? Are Iˢ and Oᶜ mutants cis or trans-acting?