Brainscape's Knowledge GenomeTM

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


See full index

asdfghjmak 2 > P1 L4 > Flashcards

P1 L4 Flashcards

1
Q

What is gene expression?

A

The transcription of genes to mRNA followed by their translation to protein

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

Why is the regulation of gene expression important?

A

To save energy - by controlling protein production.
Allows cells to react quickly - to signals like available nutrients and temperature.

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

Why is the regulation of transcription important?

A

Saves the most energy -> no mRNA synthesis
mRNA is very unstable

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

the 3 Different steps of RNA synthesis where regulation can occur

A

Initiation
elongation
termination

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

What is the role of transcriptional regulators?

A

They bind to DNA to control the transcription process at initiation

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

How is the initiation of transcription negatively regulated?

A

By transcriptional regulators that bind to the DNA
negatively:
- with the repressor (protein) that binds to the operator (DNA) and blocks transcription.
- with effectors that bind to the repressor and thus change its affinity to the DNA

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

What are effectors in the context of transcription regulation?

A

Small molecules that modulate the activity of repressors or activators.

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

Describe repression (decreasing expression)

A

Gene slicing:
In this process, a COREPRESSOR binds to the repressor and thus prevents transcription

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

Describe induction (increasing expression)

A

The INDUCER binds to the repressor, which leads to a structural change -> prevents the transcription from being cancelled

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

What is the role of allolactose in the lac operon?

A

It binds to the repressor, causing it to release from the operator and allowing transcription.

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

How is the initiation of transcription positively regulated?

A

with the ACTIVATOR (protein) that binds to the activator-binding (DNA) and transcription is activated:

  1. interaction with RNA polymerase
  2. alteration of the DNA structure at the promoter
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the difference between negative and positive regulation in transcription?

A

Negative regulation: repressor blocks or induces transcription
Positive regulation: activator enhances or represses transcription

depends on effector molecule: inducer or corepressor

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

Negative mutations

A

A mutation that inactivates the regulating gene (repressor) and thus activates transcription.

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

Positive mutations

A

The inactivation of the regulating gene (activator) prevents transcription

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

Constitutive active mutation

A

Mutations that do not react to additional signals -> often in negative regulation but rarely in positive regulation.

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

How do mutations affect negative and positive regulation in transcription?

A

Mutations inactivating repressors (negative) allow transcription, while mutations inactivating activators (positive) prevent transcription.

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

The lactose operon

A

-Regulates the degradation of lactose
-Catabolic operon
-Positive regulation: without glucose
-Negative regulation: with lactose
-LacI acts as a repressor

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

Why is the lactose operon called catabolic or degradative?

A

Because it encodes enzymes that are involved in catabolism - expression induced only when substrate is available

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

What does the Lac promoter do?

A

-sigma 70 bacterial promoter with regions: -10 and -35
-Lac I is continuously expressed -> if no lactose, it binds to lacO, close to the promoter
-With lactose: inducer binds to repressor -> change of conformation

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

What is allolactose

A

Lactose isomer -> is produced by beta-glactosidase.

21
Q

How Lac I forms a tetramer

A

It binds 2 operator sites. -> The sites (o1,o2,o3)
If o2 + o3 are removed -> repression only 20-fold instead of 1000
-If Lac I binds o1 and o2 or o3 -> Folds DNA in promoter region and stabilises.
Prevents binding of RNA polymerase to promoter

22
Q

Does the repression require the folding of the DNA and the tetramerisation of Lac I on the DNA?

A

Yes

23
Q

What are the negative repressible systems?

A

Effectors bind to repressor, which in turn binds to the operator.

Repressors that negatively control the biosynthetic operator ->is inactivated when no effector (corepressor) is present ->aporepressor

24
Q

What is the tryptophan operon?

A

-In E.coli
-Negatively repressible system. The gene TrpR (constitutive expression) encodes it.
-TrpR acts as a repressor

25
Q

Describe the negatively repressible system of the tryptophan operon.

A

-The TrpR repressor is expressed continuously and negatively regulates the operon.

-Transcription continues if no tryptophan is present -> repressor does not bind to operator site.

-If tryptophan is present: it binds to TrpR repressor -> conformational change and it binds to the operator site -> blocks RNA transcription

26
Q

Describe the positive regulation.

A

Positive regulation of transcription initiation by activators.
-Promoters, that are dependent on it, -> low affinity to RNA polymerase. -> leads to little transcription IN ABSENCE of activator

-Transcriptional activators bind DNA immediately upstream of the RNA polymerase binding site

-Inducers activate activators and corepressors deactivate them

27
Q

What is the arabinose operon

A

-in E. coli
-The genes in operon: araB,araA, araD -> are transcribed from the single promoter pBAD.
-upstream of promoter: activator region, araI
-

28
Q

What is the function of the AraC protein in the arabinose operon?

A

AraC is a DNA binding protein that acts as an activator or antiactivator depending on the presence of arabinose.

P1 - without bound arabinose - anti activator
P2 - L-arabinose is bound to araC - binds to araI and recruits RNA polymerase

29
Q

How can the activity of an activator be modified?

A

The activity of the activator can be activated by an inducer or inactivated by a corepressor.

30
Q

What is the fab operon?

A

-Positive repressible regulation
-exhibits negative inducible regulation.

-FadR = transcriptional activator and repressor

31
Q

How does fatty acyl-CoA affect FadR’s activity?

A

Fatty acyl-CoA inhibits FadR’s binding to the activator site, preventing transcription activation.
-FadR + acyl-CoA = no binding to activator site

-High levels of fatty acyl-CoA = induces expression of degredation enzymes

32
Q

What is transcription attenuation?

A

Transcription attenuation is control that functions by premature termination of mRNA synthesis.
Transcription begins at promoter but terminates in leader region.

33
Q

What influences the formation of the termination or antitermination helix?

A

Helix formation can be regulated by ribosome position, or binding: small molecules, a second RNA, or a protein.

34
Q

How can transcription attenuation be prevented?

A

can be prevented by folding RNA into alternative RNA structure - anti-terminator

35
Q

What is the role of the leader sequence in the tryptophan operon?

A

The leader sequence encodes a short mRNA with two Trp codons.
contains 4 complementary regions: RNA can fold into 2 possible secondary structures
3/4 = terminator helix
2/3 = antiterminator helix = cont transcription

36
Q

How does the position of the ribosome affect transcription in the tryptophan operon?

A

The position of the ribosome influences which RNA helices will form, affecting transcription termination.

37
Q

What happens when tryptophan levels are low?

A

When tryptophan is low, the ribosome stalls, allowing the formation of the antitermination helix 2/3 and continuing transcription.

38
Q

What occurs when tryptophan is present?

A

When tryptophan is present, the ribosome prevents the formation of the antitermination helix, allowing the termination helix 3/4 to form and stopping transcription.

39
Q

What is the function of riboswitches?

A

-Riboswitches are RNA domains that bind molecules to control translation of mRNA.
-directly sense regulatory signal
-Located at 5’ end of mRNA
-control transcription attenuation and translation initiation.

40
Q

tRNA-sensing riboswitches

A

codon-anticodon base pairing
IF tRNA is not aminoacylated => 3’ end of tRNA interacts with bulge in antiterminator => stablises => prevents termination

41
Q

small molecule binding riboswitches

A

binding of molecule directly to leader RNA => influences RNA folding + formation of terminator structure.

42
Q

How does the secondary structure of leader RNA influence gene expression?

A

some structures can protect RNA from degradation

43
Q

What are the 3 types of RNA degradation mechanisms?

A

-3’-5’ exoribonucleases
-5’-3’ exoribonucleases
-endoribonucleases.

44
Q

how do RNA degradation mechanisms work generally?

A

sequence and structure of RNA affects stability of RNA

45
Q

What is the average half-life of mRNA in bacteria?

A

The average half-life of mRNA in bacteria is 1-3 minutes.

46
Q

How do structured RNAs like tRNA and rRNA compare to mRNA in terms of stability?

A

Structured RNAs like tRNA and rRNA are very stable, while mRNAs are generally unstable.

47
Q

What is the Expression of RNAse E enzyme regulated by?

A

degradation of its own mRNA by RNAse E.
Autoregulation of expression by measuring activity of the enzyme.

RNAse E too high => transcript rapidly degraded => prevents further synthesis

48
Q
A
49
Q
A

asdfghjmak 2 (8 decks)

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