Brainscape's Knowledge GenomeTM

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


See full index

GENE221 > Module Three > Flashcards

Module Three Flashcards

1
Q

what has selection led to?

A

the evolution of efficient systems

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

what is enzyme induction?

A

bacteria only produce enzymes required for growth on a particular substrate in the presence of an inducer

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

what is the function of the promoter in a gene?

A

binds RNA polymerase and initiates transcription

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

what is the function of the operator?

A

binds regulatory proteins to alter transcription

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

what is negative regulation?

A

gene expression is turned off by a regulatory protein termed a repressor

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

what is positive regulation?

A

gene expression is turned on by a regulatory protein termed an activator

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

when is a gene expressed?

A

when the activator is active and the repressor in inactive

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

when is a gene not expressed?

A

when the activator in inactive and the repressor is active

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

what controls the lac operon?

A

a repressor protein

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

what happens to the lac operon when the activator is not present?

A

the repressor protein binds and inhibits the binding of RNA pol II

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

when is the lac operon transcribed?

A

only in the presence of lactose

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

who won the Nobel prize for discoveries concerning genetic control of enzyme and virus synthesis?

A

Francois Jacob
Jacques Monod
André Lwoff

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

what was the hypothesis surrounding inducers and gene activation?

A

that inducers that led to increased product activated a pre-existing enzyme

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

what was the beta-galactosidase, inducer experiment?

A

an inducer was added and the amount of beta-galactosidase increased

when the inducer was removed the synthesis stopped

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

what is the inducer of the lac operon?

A

Lactose is an inducer (allolactose)

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

what else can act as an inducer of the lac operon?

A

IPTG is a related molecule that is not a substrate and can be used as an inducer of the lac operon

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

what are the genes contained within the lac operon?

A

lacZ
lacY
lacA

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

what did the PaJaMo Experiment find?

A

The I+ allele could repress b-gal in the presence of I-

The I+ (wild-type) was dominant over I-

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

which lacI is dominant?

A

lacl+ is trans-dominant over lacl-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what encodes for a diffusible repressor of the lac gene?

A

lacl

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what happens in the presence of lacl+ and lacl_?

A

lacl+ encodes for the repressor which can bind both genes

gene is not expressed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what happens in the presence of lacl^s?

A

lacl^s mutants do not express lacZ, lacY or lacA

lacl^s is dominant over both lacl+ and lacl-

the repressor cannot bind the inducer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how do O^c mutants affect the binding of repressors?

A

the repressor cannot bind to the mutant operator (O^c)

the gene is expressed even in the presence of an inducer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is a virus?

A

an infectious agent that must grow or reproduce inside a host cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what is a virus composed of?

A

nucleic acid, genetic material and protein coat (some also contain lipids in their coats)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

what is a bacteriophage?

A

Viruses that infect bacterial cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is phage lambda?

A

an phage that infects E.coli

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what are the features of phage lambda?

A

Double stranded DNA genome (dsDNA)

Long flexible tail, icosahedral head

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what does the lifecycle of phage lambda depend on?

A

depends on the state of the host bacterium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is the lytic lifecycle?

A

results in the lysis of the bacterial cell upon release of progeny phage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is the lysogenic lifecycle?

A

results in the stable carriage of the phage (prophage) within the host cell (lysogen)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is a virulent phage?

A

A phage that is only able to undergo replication via the lytic cycle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what is a temperate phage?

A

A phage that can replicate either in the lytic or lysogenic cycles

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

what is a lysogen?

A

a host cell that is harbouring a prophage during lysogeny

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
35
Q

what is a prophage?

A

the latent for of a temperate phage that remains within the lysogen

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
36
Q

what are the important events in the lambda phage lifecycle?

A

infection
decision (lytic or lysogenic)
maintenance
induction or ‘switch’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
37
Q

what are cos sites?

A

cohesive end sites

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
38
Q

what is the structure of the genome in a phage head?

A

the genome in linear

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

when does the genome of the phage circularise?

A

following injection

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
40
Q

what are the steps in phage assembly and release?

A
  • head and tail proteins are synthesised
  • DNA is packaged into heads
  • tails are added
  • the host is lysed releasing new phage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

what are the steps in phage integration and maintenance?

A
  • lambda intergrates
  • prophage is stably maintained
  • prophage passed to daughter cells
42
Q

what are the sites where integration occurs between the phage and bacterial chromosome?

A

attP (attachment on Phage)

attB (attachment on Bacteria)

43
Q

what is the enzyme that integrates the phage into the bacterial chromosome?

A

Integrate

44
Q

when is it a good time to make more phages?

A

High growth of bacteria, plenty of food/energy

45
Q

when is it a good idea to integrate into the genome?

A

If the bacterial cell in unlikely to have the resources to produce many more phages

46
Q

when is it a good time to leave the lysogenic cycle and enter the lytic cycle?

A

if the host cell is damaged and likely to die

47
Q

what is the Cro protein?

A

Expressed early in infection and the major player in establishing lytic growth

48
Q

what is the promoter that produces N protein?

A

PL

49
Q

what is the promoter that produces Cro protein?

A

PR

50
Q

what is N protein?

A

an anti-terminator protein that enables transcription past 2 terminators resulting in early gene expression

51
Q

what are the phage genes involved in DNA replication (lytic growth)?

A

O and P

52
Q

what are the phage genes involved in Recombination (integration)?

A

int and xis

53
Q

when are the proteins for the lytic and lysogenic pathways produced?

A

proteins for both pathways are produced early before the phage has decided which cycle to enter

54
Q

what is the nut site?

A

N utilization site

55
Q

What is cro?

A

a DNA-binding protein that represses transcription

-cro promotes the lytic cycle

56
Q

what is CII?

A

CII is a DNA-binding protein that activates transcription

-promotes the lysogenic cycle

57
Q

what is CI?

A

is a DNA-binding protein that can activate or repress transcription

  • Cl activates it’s own expression
  • Represses genes required for lytic cycle
  • maintain lysogeny
58
Q

what protein promotes the lysogenic pathway?

A

Cll

59
Q

what protein promotes the lytic pathway?

A

Cro

60
Q

what is the deciding protein for which lifecyle the phage will enter?

A

Cll

61
Q

what is the roll of Cll in deciding which lifecycle that phage will enter?

A

Host protease degrade Cll
Healthy cells produce high levels of protease
In actively growing cells, Cll gets degraded

62
Q

when does the cell enter the lytic cycle?

A

in actively growing cells Cll is degraded and so there is lots of Cro protein and this promotes the lytic cycle

63
Q

what is Q?

A

Q is an anti-terminator than enables expression of late lytic genes (head, tail and lysis genes)

64
Q

when does a phage enter the lysogenic lifecyle?

A

starved cells produce less protease and so the Cll is not degraded
This promotes entry into the lysogenic cycle

65
Q

What does Cll activate in the phage?

A

int and Cl repressor

66
Q

what does int activation result in?

A

intergration of lambda into host chromosome

67
Q

what does Cl repressor do?

A

activates its own expression and binds to OL and OR to repress all other phage genes

68
Q

how is lysogeny maintained?

A

by Cl

69
Q

how does Cl protein maintain the prophage?

A

Cl is a repressor of all phage genes but an activator of itself
Keeps the phage genome ‘silent’ in bacterial chromosome until induction

70
Q

what promotes the lytic cycle?

A

Cro represses cl

Q anti-terminates lytic genes

71
Q

what promotes the lysogenic lifecycle?

A

Cll activates cl and int

72
Q

what types of plaques does lambda form and why?

A

Lambda forms turbid plaques due to lysogens being immune to further infections

73
Q

what protein maintains lysogeny?

A

Cl

74
Q

how does Cl maintain lysogeny?

A

Cl is a repressor of all phage genes but an activator of itself

keeps phage genome ‘silent’ in the bacterial chromosome

75
Q

what are the basic components of the switch?

A

Regulatory proteins Cl (repressor) and Cro

Operator sites on the phage DNA and their promoters

RNA polymerase (essential for transcription

76
Q

what are the two positions of the switch?

A
  1. Lysogeny: Cl on and Cro off (maintenance)

2. Lytic: Cl off and Cro on (induction)

77
Q

what are the three operator sites for Cl and Cro?

A

OR1, OR2, OR3

78
Q

what are the two promoters for RNAP?

A

PRM
PR
-do not overlap

79
Q

What is RNAP?

A

RNA polymerase

transcribes DNA into RNA and is provided by the bacterial host

80
Q

where does RNAP bind in the switch?

A

to either PR or PRM but never to both

PR activity with RNAP does not need a regulatory protein

PRM needs Cl as an activator

81
Q

what happens when RNAP is bound to PRM?

A

Cl is activated

Lysogenic cycle is maintained

82
Q

what happens when RNAP is bound to PR?

A

Cro is activated

The lytic cycle is induced

83
Q

what are the features of the operators?

A

17bp long

similar to each other but Cl and Cro can distinguish between them due to different affinities

84
Q

how do Cl dimers bind to DNA?

A

using their N-terminal domain

85
Q

where do Cl dimers bind to DNA?

A

to one OR along one side of the DNA helix

86
Q

what is negative control with Cl?

A

Cl at OR2 turns off cro gene by preventing RNAP from binding to cro promoter (exclusion)

87
Q

what is positive control with Cl?

A

Cl at OR2 helps RNAP bind and begin transcription of cl gene

88
Q

what are the two functions of cl?

A

negative control

positive control

89
Q

what are the two factors that contribute to Cl binding?

A
  • intrinsic affinity

- Cooperativity

90
Q

when is the affinity for Cl increased?

A

When Cl is bound at OR1 it increases the affinity at OR2

91
Q

What is the affinity for Cl at OR3?

A

weak and no cooperativity

92
Q

How does the cooperative binding of Cl work?

A

Dimers of Cl ‘lean’ towards each other

93
Q

Why does cooperative binding not occur at OR3?

A

the Cl C-terminal domains are unavailable

94
Q

what is the binding of Cl in the maintenance of lysogeny?

A

Cl is bound at OR1 and OR2
This inhibits cro and maintain expression of cl

This state is very stable and inherited by daughter cells after cell division

95
Q

what is induction?

A
  1. prophage excises from the host chromosome

2. Lytic growth

96
Q

what can cause induction?

A

UV light

97
Q

how does UV cause induction?

A

the operator sites are cleared of Cl by activated RecA

98
Q

where do cro dimers bind?

A

to each OR site in the absence of Cl

Cro binds on one side of the DNA helix

99
Q

What is the structure of Cro?

A

cro has a single domain
Two monomers or cro from dimers

almost all cro in the cell is dimeric

100
Q

how does cro bind to the DNA?

A

cro binds to each operator site independently

101
Q

when is possible Cl expression stoped?

A

when Cro is bound to OR3

GENE221 (6 decks)

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