Brainscape's Knowledge GenomeTM

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


See full index

BIOL332 > Gene Regulation > Flashcards

Gene Regulation Flashcards

1
Q

Examples of Transcriptional gene regulation

A
  1. Lac Operon
  2. Trp Operon
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Gene Expression

A

The process that heritable information in a gene is made into a functional gene product (Protein or RNA)

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

Gene Regulation

A

The process of controlling gene expression

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

Where can the mechanisms of gene regulation occur

A

Can occur during any part of gene expression

Includes:
1. Transcription
2. RNA processes
3. Translation
4. Post translational modifications

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

Euk RNAs + regulation

A

Eukaryotic RNAs have introns that need to be spliced –> controlling gene expression can occur during processing of RNA

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

Translation Regulation

A

Sometimes proteins are non-functional when first translated – need to be modified to function

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

Gene regulation in bacteria

A

In bacteria – regulating gene expression is mainly done at the transcriptional level

***Bacteria – Transcription + translation are couples = most of bacteria gene regulation is at the transcriptional level

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

Lactose Metabolism

A

Background: Preferred energy source in bacteria = glucose

IF no glucose THEAN bacteria can use other energy sources such as Lactose

Lactose –> Galactose + glucose

***It is more effective to use glucose if have glucose –> if you have glucose then won’t make the enzymes required to turn on lactose pathway when lactose is present

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

Prefered energy source in bacteria

A

Glucose

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

Genes on Lack operon

A

LacI
CAP binding site
Promoter
Oportaor
LacZ
LacY
LacA

Lac Z, Y, A = Invloved in lactose metabolism –> Transcribed together same mRNA –> OPERON
- Each (LacZ, LacY, LacA) have own ribosome binding site

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

Constitutive Gene expression

A

Expressed all of the time at constant levels

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

Lac Z

A

Codes for B-galactoside – enzyme that converts lactose to alolactose + galactose + glucose

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

LacY

A

Codes for Lactose permease – protein that allows lactose to enter the cell

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

Lac A

A

Do not know what it codes for – knock out doesn’t seem to have effect

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

Opator in Lac Operon

A

Between Promoter + Lac Z –> have operator domain

Function: Where repressor can bind to

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

CAP binding site

A

In Lac operon – upstream of promoter

Function: Place where CAP can bind

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

Operon

A

Multiple coding regions on same mRNA

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

Expression of LacI and CAP

A

LacI + CAP = expressed at consistent levels throughout cell = constitutive gene expression

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

Promoter in Lac operon

A

Upstream of LacZ gene
- When RNA polymerase binds to promoter – transcribed and get 3 genes
+1 start site is just downstream of this

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

Regulatory genes in Lac operon

A
  1. Lac I – ecodes lac repressor
    • Upsteam of Lac operon (not officially part of lac operon – has its own promoter + creates own transcript)
  2. CAP – Catabolic activator protein
    • Found elsewhere on the circular chromosome – has own promoter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Lac operon repressor (Overall)

A

No lactose –> Lac repressor binds = no transcription

Yes Lactose –> Allolactase binds to repressor = induce transcription

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

Lac operon repressor

A

Repressor = can bind to operator sequence

WHEN binds it gets in the way of RNA polymerase that is trying to sit on the promoter and induce gene expression

When repressor is bound to operator = transcription is blocked

WHEN lactose is present –> Some amount of the lactose is converted to allolactose –> Allolactose can bind to the repressor = prevents the repressor from binding to the Operator site = NOW RNA polymerase can sit on the promoter and begin transcription

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

Promoter + Operator sequnce of Lac operon

A

Promoter has:
-35 abd -10 sequence

+1 start site = beginning of the operator sequence

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

Transcription of Lac Operon

A

RNA polymerase = begins to transcribe the Lac operon BUT repressor bound to the operator sequence prevents +1 from being accesible to RNA polymerase = blocks transcription

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

Type of regultion in Lac Operon

A

Lac operon = example of negative regulator

***Uses negative regulation to control gene expression

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

Negative Regulation

A

When binding of regulatory protein blocks transcription

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

Allolactse is an

A

Inducer – A small molecule that activates gene expression

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

Induce

A

A small molecule that activates gene expression

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

CAP in Lac Operon

A

CAP/cAMP complex – when bound CAP binding site = RNA polymerase is recruited to the promoter sequence = get HIGH transcription
- Promotes transcription

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

CAP activation

A

When CAP is transcribed into a protein CAP is inactivated in the current form BUT when bound to cAMP = CAP can bind to the CAP binding site

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

cAMP

A

A signaling molecule produced by glucose metabolism

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

Glucose level vs. cAMP level

A

Glucose is high = cAMP is low –> no cAMP = no bind to CAP binding site

Glucose is low = cAMP is high –> can bind to CAP binding site = get transcription

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

CAP Binding to CAP binding site

A

CAP binding to CAP binding site = causes DNA to loop around = making -10 and -35 more accesible to RNA polymerase –> RNA polymerase is recruited to the promoter = get transcription

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

Image of Lac operon

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

What type of regulator is CAP

A

CAP is an example of a positive regulator

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

Positive regulation

A

When binding of a regulatory protein activates transcription

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

cAMP is an…

A

Inducer – cAMP allows CAP to bind to the binding site

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

Overall Lac operon

A
  1. Lactose + No glucose = Highest transcription
    • Lactose = have allolactase –> Allolactase binds to Repressor = prevents the repressor from binding to operator = get transcription
    • No glucose = cAMP increases = CAP binds to cAMP = CAP binds to the binding site = recruits RNA polymerase = transcription occurs
  2. Lactose and Glucose = some transription – Even though CAP is not helping bring RNA polymerase to promoter RNA polymerase can still find promoter and and produce some transcript
    • Glucose is high = low cAMP = CAP won’t bind to recruit RNA polymerase
    • Lactose = have some allolactose to bind to repressor
  3. NO Lactose + Glucose = No transcription
    • No Lactose – repressor binds to operator
    • High glucose = low cAMP = CAP won’t bind to site = not recruiting RNA polymerase
    • No RNA polymerase + repressor blocking transcription = No transcription
  4. No Lactose + No glucose = No transcription
    • No glucose = high cAMP = CAP binds to CAP binding site
      BUT
    • NO lActose = reprssor is bound to operator = even though RNA polymerase is being recruited the reprssor is blocking transcription –> repressor is good at blocking transcription = when reprssor is bound even when have CAP = transcription is blocked
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
39
Q

Exception in No Lactose + No glucose

A

Have leaky expression – will produce a few transcripts
- Transcripts can sneak off = small amount of product = leaky expression

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

Putting Lac Operon together

A

Start with No lactose BUT reprssor binds to operator sequence because of leaky gene expresses small amount of B-galactosidase + Lactose permase will be produced

Lactose present can enter the cell through lactose permease – in cell B=Galasidase can convert it to allolactase

Allolactase binds to reressor = falls off operator –> promotes transcription of operon = produce more B-galactosidase + permase

Transcription of operon continues and make permase + B-galactosidease as long as lactose is present in the media

When cell runs out of Lactose = no allolactor = repressor binds to operator and prevents transcription

Over time proteins will be degraded –> go back to small amount of permase + galactosidase because of leaky expression

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
41
Q

What is the Trp operon an example of

A

Example of gene regulation through attenuation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
42
Q

Tryptophan

A

Essential Amino Acid

***Sleep inducing compound after eating Turkey

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
43
Q

Producing Tryptophan

A

Mammals can’t produce own Trp – need to be obtained through foods BUT bacteria can synthesize Trp

E.coli – the enzymes used for Trp Synthesis = found in Trp operon

Bacteria – can also use Trp that they find in the environment –> they don’t always need to produce enzymes involved in Trp synthesis = Trp operon is regulated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
44
Q

Regulation of Trp Operon

A

Expression of the Trp Operon is regulated in 2 ways:
1. Negative regulation (using a Co-repressor)
2. Attenuation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
45
Q

Trp Operon (gene)

A

Trp repressor – Translates into protein Trp Repressor
- Represor gene (not on Trp operon)

Promoter – recruites RNA polymerase to produce RNA

Operator – Where Trp reprssor binds

Trp Leader peptide – Transcribed to mRNA (Part of annetuation process)

5 genes that encode enzymes needed for Trp Biosynetshsis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
46
Q

5 genes that encode enzymes needed for Trp Biosynetshsis

A

Co transcribed on the same RNA = p[eron of Trp Biosynthesis genes

Once they are translated to proteins – the proteins are part of complex required to convert Chorsimate to Trp

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
47
Q

Trp repressor regulation

A

Trp Repressor can’t bind to operator sequence – it id in inactuve form when it is first translated into protein

THEN Trp can bind to Trp repressor – when binds = activates represor = allows represor to bind to operator sequence

When bound RNA polymerase might be recruited to the promoter but it can’t push represor = No transcription of downstream genes

Overall: Lowers transcription – lowers amount of transcript by 70%

48
Q

Trp Repressor form of regulatino

A

Negative regulation – Bound regulatory protein prevents transcription of downstream genes

***one of the two steps involved in regulating Trp biosynthesis

49
Q

Trp is a …

A

Co- repressor – because Trp and Trp repressor binds to operator

50
Q

Trp Repressor regulation (Overall)

A

Trp is low = Transcription is High

Trp us high = Transcription is low

51
Q

Transcription + Translation in Bacteria

A

Transcription + Translation are coupled – RNA polymerase produces a transcript that is being co-translated before transcripts are done being made

***Important for second regulatory step of attenutation in Trp operon

52
Q

Attenuation Definition

A

To lower affect of something – Lowers expression of genes

53
Q

What does Attenuation use in Trp Operon

A

Attenuation = accomplished through Trp Leader peptide (TLP)

54
Q

TLP structure

A

RNA produces has TLP – has 4 regions of TLP THEN stop codon

TLP = only 14 Amino Acids long

55
Q

Region in TLP

A

Regions have complementary sequences to each other –> Complementary sequences can form stem loop structures in the mRNA

MEANS – there are 2 possible secondary structures that are formed in the mRNAs

56
Q

Secondary structures formed in mRNA

A

2 possibilities:
1. Attenuation form –> When Stem loop structure is formed between regions 3 and 4 AND between 1 and 2

  1. Anti-Termination –> Stem loop between regions 2 and 3
57
Q

Region 1 in TLP

A

Region 1 contains 2 trp codons (Need tRNA with Trp to produce TLP)

58
Q

Attentuation When Trp levels are high

A

Ribsome binds to initate protein synthesis of RNA emerging from RNA polymerase – because have Trp in cells = have charged tRNA with trp ready for protein synthesis

Ribosome can produce the peptide of TLP including the trp residues encoded by Trp codons in region 1

As ribsome goes down mRNA it covers 1 and 2 region of the LPS

Polymerase is ahead – transcaribes regions 3 + 4 –> regions 3 + 4 can form Stem Loop while the ribosome is completing translation

Stem loop of 3 + 4 = followed by a series of U resides

Stem loop + poly U sequences (AT rich region) = forms transcription termination sequence = allows RNA polymerase to fall off transcript = prevents transcription of things down stream

***Rho independent form of transcription termination

59
Q

Attentuation with high trp (Overall)

A

High Trp = have charged tRNA high = Ribosome produces protein to make LPS = Stem loop forms between 3 + 4 = Stop Trp synthesis
- High Trp = Terminated = not produces Trp Biosynthesis enzymes
- High Trp = attentuation structure is encouraged in RNA = causes termination of transcript

60
Q

Attenuation - Low Trp levels

A

Ribosome will binds to the newly synthesized mRNA and begin to produce the LPS BUT when reaches Trp codons in region 1 –> ribsome requires charged tRNA with Trp residue

BUT since in low Trp = most tRNA won’t have Trp AA avalable to put into LPS –> Ribosome is stalled siting on region 1 waiting for charged tRNA

RNA polymerase is transcribing and continues to transcrived regions 2 + 3 + 4 –> regions 2 + 3 can form stem loop structure – forms anti-attentiation structure

When Anti-attentuation structure is formed the terminater signal made by 3 + 4 = can’t signal the end of transcription = RNA polymerase will continue transcribing genes TRP e,d,c,a

61
Q

Low Trp Levels Attentuation overall

A

Promote stalling of ribosome = promotes formation for anti-attenutaion strucure = allow transcription to proceed

62
Q

Regulation of Trp Operon (overall)

A

Trp is low –> Transcription proceeds – enzyme synthesis occurs allowing Trp biosynethsis
- Trp repressor = inactivated = allows transcription to proceed
- Anti antenuation structire on mRNA = allow transcription to proceed

Trp is high
- Activates trp repressor = allowing it to bind to operator = prevents transcription
- Have attenuation structure on mRNA –> Produces Stem loop termination sequqnece early = transcription is halted = no enzyme syntehsized = cells won’t produce Trp

63
Q

How much does Trp repressor prevent Transcriotion

A

Prevents 70% of transcription = need additional regulation to reduce transcription level

Additional regulation - accomplished by promoting attenuation structure

64
Q

What is Trp an example of

A

The Trp operon is an example of how attentuation regulates gene expression by controlling transcription

65
Q

Use of Attenuation

A

Transcriotional regulation through attenuation is widely used in Prokaryotes + Archea
- Level of transcriptional regultions is used in prokaryotes + Archea = suggests it is evolutionary ancient mechanism of gene regulation

66
Q

Second use of attenuation

A

Attenuation might also be used to regulate protein translation –> IF mRNA makes attenuation structure that involoves the Ribosome binding site –> could prevent the ribsome from binding to mRNA = block translation

***Active area of reserach – looking for genes regulation by attenuation to conrtol translation

67
Q

Attenuation (Euk)

A

Attenuation might be important mechanism of gene regulation in Euk where transcriotion + Translation are not couples

68
Q

Gene regulation Eukaryotes

A

Mechansim leveles of gene regulation in Eukaryotes is much less well understood

69
Q

Themes in biology

A

Themes in biology tend to repeat themselves –> things learned in lac operon can be inform us about how more complex beings regulate gene expression

70
Q

What does the LacOperon and The Trp Operon show is

A

The Lac Operon and the Trp Operon show us examples of what can be used to regulate gene expression

71
Q

Why doe organisms need to regulate gene expression

A
  1. Cost energy to make proteins
  2. If expressed all proteins then the cell would be overloaded (no space)
  3. Different organs and tissues need different thinks
  4. Need different things in different environments
72
Q

Genes that are not regulated

A

Not all genes are regulated – some are on all of the time (Constitutive genes)

There are things that we always need

Example - Ubiquitin + ATPase + RNA polymerase + Oxidative phosphorylation + Histones + Ribosomes + DNA repair paths + Cell cycle enzymes

73
Q

Ways to regulate gene activity

A
  1. Transcription - block transcription (Block or alter transcription rate)
  2. Translation
    • Block or change translation rate
    • Change mRNA life span (stability) – could degrade RNA (block translation by getting rid of mRNA)
  3. Post-tranlation – modify proteins to activate or inactivate (chemical modifications)
74
Q

If you were a bacteria - what would be the most efficonet way to turn off a specific gene

A

Block Transcription – save energy (not making transcript OR protein)

ALSO it is hard to block all transcripts from being translated (one can be translated and make lots of proteins)

75
Q

1 DNA makes

A

1 DNA makes many transcripts

1 Transcripts makes many proteins

76
Q

Glucose

A

Easy energy source – goes through glycolysis to make pyruvate

***ALL other energy sources require more ATP input and or fewer ATP output

77
Q

Lactose

A

Alternate energy source

Overall:
Brought in by Lactose Permase THEN Lac Z that makes B-galactosidase
B-galactosidase = coverts lactose –> Glucose + galactise
- Side product = Makes allolactase – can be converted to glucose

78
Q

B-galactosidase

A

Lactose –> glucose + galactose
AND
Lactose –> Allolactase

79
Q

Lac operon (overall)

A

Lactose and no glucose –> ++++ – Tons of expression

Lactose and glucose –> ++ – Little expression
- Prefer glucose but uses some lactose

No Lactose and no glucose –> +- – no expression but have leaky expression

No Lactose and Glucose –> – no expression

80
Q

Lactose effect on Lac operon

A

Lactose induces expression of the Lac operon

81
Q

How does Lac Operon sense the presense of Lactose

A

Sense the presence of lactose through allolactose

82
Q

Lac repressor binding to operator

A

Lac repressor binds to operator sequence with high affinity (binds tightly)

***When bound RNA polymerase can’t find the transcription start site – covers start site
- RNA polymerase goes to the -10 and -35 elements but can’t do anything

83
Q

Positive vs. Negitive regulation

A

Positive – Protein binds and promotes transcription

Negative – protein binds and prevents transcription

84
Q
A

Answer: Negitive regulator

85
Q
A

Answer: Not bound to the operator

86
Q

Use of cAMP

A

Activates genes when low glucose

87
Q

How does CAP recruit RNA polymerase

A

CAP bound to the CAP binding sequence –> taunts RNA polymerase by exposing -10 and -35 regions

***Promotes expression by exposing promoter to RNA polymerase

88
Q
A

Answer: Positive Regulation

89
Q

Lac Operon Outcomes (Summary)

A

Lactose + No glucose – Highest level of transcription
- Low glucose = High cAMP = CAP bound –> Transcription
- Lactose –> Have Allolactose –> Repressor = not bound –> Transcripotion

Lactose + Glucose – Some transcription BUT lower
- High lactose –> Repressor not bound –> Transcription
- High glucose = low cAMP = CAP Not bound –> No transcription

No Lactose + No glucose –> No transcription BUT leaky expression
- No lactose = repressor bound –> No transcription
- Low glucose = High cAMP = RNA polymerase is recruited byt repessor is good at blocking BUT sometimes RNA polymerase goes befire repressor gets there = get transcription before reprssor –> make some protein = get some expression

No lactose + glucose – No Transcrioption
- High glucose = CAP not bound –> No transcription
- No lactose = No allolactose = repressor bound –> no Transcription

90
Q

Leaky Expression

A

There is some basal very low level of expression

91
Q

How does Leaky expression work

A

No Lactose + No glucose –> No transcription BUT leaky expression
- No lactose = repressor bound –> No transcription
- Low glucose = High cAMP = RNA polymerase is recruited byt repessor is good at blocking BUT sometimes RNA polymerase goes befire repressor gets there = get transcription before reprssor –> make some protein = get some expression

***One transcript can be translated multiple times allow a small amount of protein expression

92
Q

Lac Operon cycle

A

Start = no Lactose + get some B-galactosidase

THEN – add lactose –> Lactose enters the cell through Permease AND the lactose gets converted to allolactose by B-galactosidase

THEN Repressor not bound = get more expression = more allolactase = more repssors fall off = increase operon expression

THEN use all lactose = no more allolactose = repressor binds = block transcription

THEN Proteins are degraded expect some leaky expression = have some amount of proteins

93
Q

Why might it be benefical to have leaky expression

A

If off all of the way and want to turn on in presence of lactose need some B-galactosidase to start the cycle

Overall: Hard to trun something off entriley

94
Q
A

Answer: Constitutive

Repressor can’t bind = will get transcription all of the time

95
Q
A

Answer: Repressed – Can’t make allolactose = repressor bound = always repressed

96
Q

Use of Lac Operon

A

Lac Operon = provides lots for biotechnology + medicine

97
Q

Biotech use of Lac operon

A

Can engineer bacteria o express insiulin under the lac promoter/operator
- IPTG = mimics allolacase causing LacI to fall off the operator
- Engineer plasmid to have a prmoter + operator –> Add LacI repressor = get no insulin
- Making insulin costs energy = want no insulin to be made when the cells are young THEN add IPTG to knock repressor off THEN cells will start to make insulin
- Use Lac operon to turn on/off

***Can be adapted to any gene

98
Q

Monitoring gene expression in Lab

A

Can use Lac Z – can see when something is turned on (when gene is on it turns blue)

Cells can be engineered to express B-galatosidase under any promoter of interest

THEN add X-galactose and you can visualize the cells that are expressing LacZ (and infer about the regulation of the gene of interest)

99
Q

Affintioty of Trp Repressor

A

Have low transcriptions BUT repressor has low affinity for operator = can be knocked off = can get some transcription but at a low rate

100
Q

Probability of Trp codons next to each other

A

2 Trp next to each other is rare – used for regulation

101
Q

Where is attenutaion used

A

Not limited to bacteria

102
Q

Gene regulation Tool Kit

A

Activator – A regulatory protein that promotes gene expression

Repressor – A regulatory protein that prevents gene expression

Inducer – A small molecule that promotes gene expression

Co-repressor - a small molecule that prevents gene expression (typically works with a repressor)

Signalling molecule – a small molecule that transmits signals to regulatory systems (cell communication)

Regulatory Sequence – Sequences on DNA/RNA that control gene expression (Ex. promoters + operators + CAP binding site)

103
Q
A
104
Q
A
105
Q
A

High Trp = turn off operon because induce termination sequence in RNA

***In living cells don’t get stem loop between 1 and 2 because ribosome is covering them

106
Q

Transcription Termination (pro)

A

Transcription ends when a Stem Loop structure forms in the RNA followed by AT rich sequence – Need AT rich region after

***If just Stem loop then RNA polymerase won’t fall off

107
Q

High vs. High Trp

A
108
Q

Trp Operon sequence

A

TRP –> region 2 –> Region 3 –> Region 4 –> AT rich (lots of U)

109
Q
A

Trp repressor – Will bind sometimes – some Trp = when find bind but not a ton = sometimes won’t bind –> somtimes blocked

Trl RNA structure formed –>
- Sometimes have tRNA = get attenuation structure
- Sometimes ribsome waits = SL 2 + 3 = Get anti attenutaion structure

Overall Expression – moderate

110
Q

Lactose vs. trp expression

A

Lac operon = don’t want to express if have no lactose = no expression

Trp = you always have moderate expression

111
Q

Use of Attenuation

A

Allows fine tuning of trp in cell

Better than waiting for an all or nothing approach to gene regulation

112
Q
A

Answer: Get Anti-attenuation structire –> Promote transcription (ribosome stalls)

***System is no longer regulation by Trp – plays on

113
Q

Positive vs. Negitive feedback loop

A

Positive = Product promotes expression to make more product

Negative = Product prevents more product from being made – product represses

114
Q

Loop in Trp synthesis

A

Negative feedback loop – If increase Trp then repressor binds AND get attenuation structure

115
Q

Loop in Lac Operon

A

Overall: Positive feedback

Increase lactose = increase allolactase = no repressor = get transcription THEN –> Increase Lac Z make allocatase = activate transcription more

Increase all = increase transcription = positive feedback loop because when produce Lac Z = produce more of what you need to get transcription

116
Q

Moleculare in Trp Operon

A

Repressor –> trp Rpressor

Co-repressor –> Tro

Regulatory sequences –> Operator + Promoter +

***Trp Leader peptide = Don;t know – can argue part of regulatory sequence

BIOL332 (25 decks)

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