Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Microbio Exam 2 > Lecture 8 (Regulation of gene expression and quorum sensing) > Flashcards

Lecture 8 (Regulation of gene expression and quorum sensing) Flashcards

1
Q

What is the importance of gene regulation?

A

To ensure that genes are only active when their protein product is needed by the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

T/F: Sometimes cells regulate the conversion of genes into proteins

A

T

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

T/F: Both prokaryotes and eukaryotes organize collections of genes into operons

A

T (only some eukaryotes, though)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

All genes within an ______ contribute to a single-cell function

A

operon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Operons can be _______ or ________

A

Inducible, repressible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is an inducible operon?

A

Exists in the “off” state, but can be turned on

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is a repressible operon?

A

Exists in the “on” state, but can be turned off

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are the 2 types of genes found in operons?

A

1) Structural genes
2) Regulator genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are structural genes?

A

1) They code for proteins needed for normal cell operation
2) Ex: enzymes and virulence factors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What are regulator genes?

A

They code for proteins that regulate other genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

T/F: genes encoding catabolic enzymes are often found in inducible operons

A

T (the operon is turned on when the substrate of the enzymes is available)

EX: for the lac operon, the gene for beta-galactosidase is turned on when lactose is present

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What type of operon is the lac operon?

A

Inducible

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the reaction of the lactose?

A

Lactose –(beta-galactosidase/lactase)–> Galactose + glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

T/F: genes encoding for anabolic enzymes are often in repressible operons

A

T (ex: arg operon, the operon is turned off when the product of the enzyme builds up)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the reaction that produces arginine (arg operon is turned off)

A

Citruline + aspartate –(Arg synthetase)–> arginine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the 5 features of an operon?

A

1) Regulator
2) Repressor
3) Promoter
4) Operator
5) Structural genes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What function does the regulator serve in the operon?

A

the gene that encodes the repressor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What function does the repressor serve in the operon?

A

1) An allosteric protein that binds to the operator DNA
2) Has a binding site for DNA and a binding site for another molecule
3) When one binding site is occupied, it changes the shape of the other binding site

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What function does the promoter serve in the operon?

A

Recognized and bound by RNA polymerase

20
Q

What function does the operator serve in the operon?

A

Contains the “on/off” switch

21
Q

What happens when the inducible operon remains in its normal off position?

A

1) The repressor binds to the operator sequence
2) RNA Polymerase does NOT bind to the promoter
3) No transcription, no translation

22
Q

What happens when the inducible operon is in the “on” position (ex: lac operon)?

A

1) In the absence of lactose, the repressor binds to the operator
2) When lactose (the substrate) is available, it binds to the repressor and causes it to dissociate from DNA
3) RNA polymerase binds
4) Transcription -> translation

23
Q

What happens when the repressible operon remains in its normal turned-on position?

A

1) The repressor is inactive (wrong shape to attach to operator)
2) RNA polymerase binds
3) Transcription -> translation

24
Q

What happens when the repressible operon is in the “off” position (ex: arg operon)?

A

1) When arginine builds up, it binds to the repressor
2) The repressor changes shape and binds to the operator
3) No transcription, no translation

25
Q

T/F: Gene regulation can be a complex process involving multiple regulators

A

T (ex: OB-PrfA network in Listeria monocytogenes)

26
Q

What are the 2 regulators in the OB-PrfA network in Listeria monocytogenes?

A

1) OB = alternative sigma factor (activates “stress response” genes and virulence genes)
2) PrfA = virulence regulator (activates virulence genes)

27
Q

When are the stress response and virulence genes turned on for Listeria monocytogenes?

A

When the bacterium enters a host cell (otherwise not harmful when found in soil)

28
Q

OB alternative sigma factor

A

1) Stress regulator activated by pH fluctuation
2) Positively regulates/”turns on” prfA
3) Positively regulates acid response genes and some genes that help infect other cells

29
Q

prfA virulence regulator

A

1) Virulence regulator activated by temperature
2) Positively regulates genes that help infect other cells

30
Q

What temperatures influence prfA?

A

1) Between 30ºC-37, prfA is expressed
2) prfA protein is only made at 37ºC

31
Q

What happens with prfA when the temperature is 37ºC (human body temp)?

A

1) Secondary structure “melts”
2) Ribosomes are now able to bind
3) PrfA protein can be made
4) Virulence gene expression occurs

32
Q

When does quorum sensing occur?

A

When a bacterial population reaches high concentrations (a quorum)

33
Q

Quorum sensing (QS) is a type of _________ _________.

A

bacterial communication

34
Q

What happens when a bacterial population reaches a high concentration (a quorum)?

A

They use QS to coordinate behavior via coordinated gene expression (QS can “turn-on” gene expression)

35
Q

Quorum sensing is critical for _______ formation

A

biofilm

36
Q

T/F: Only some bacteria are capable of quorum sensing

A

F (all bacteria are capable of QS)

37
Q

Quorum sensing bacteria produce ________ molecules and contain _________ for them

A

inducer, receptors

38
Q

T/F: QS bacteria contain QS-regulated genes

A

T

39
Q

T/F: inducer molecules are always produced at low levels

A

T (constitutive production)

40
Q

Inducer molecules _______ into and out of the cell

A

diffuse

41
Q

What happens with QS when bacteria replicate to high numbers (a quorum)?

A

1) The inducer molecules reach a threshold concentration and communication between cells begins
2) The inducer-receptor complex binds to DNA and turns on target genes

42
Q

What are some possible genes that may be activated due to QS?

A

1) Biofilm formation (E. coli, pseudomonas)
2) Polysaccharide production (E. coli, pseudomonas)
3) Virulence
4) Antibiotic resistance
5) Antibiotic production
6) Light emission (Vibrio harveyi)

43
Q

What operon in Staphylococcus aureus regulates biofilm synthesis?

A

ica operon (inducible operon)

44
Q

What is the inducer for the ica operon?

A

Autoinducer-2 (AI-2(

45
Q

What happens to the ica operon in the absence of AI-2?

A

1) Repressor binds to the operator
2) RNA pol. not able to bind
3) No polysaccharide production

46
Q

What happens to the ica operon in the presence of AI-2?

A

1) AI-2 binds to and relieves the repressor
2) RNA able to bind
3) polysaccharide production can occur

Microbio Exam 2 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions