Brainscape's Knowledge GenomeTM

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


See full index

PM 228 - Gene expression > Lecture 7 - Lambda page > Flashcards

Lecture 7 - Lambda page Flashcards

1
Q

Compare lambda phage and T-phage

A

They are similar but the tail section is relatively longer in lambda phage

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

Compare lambda phage and T-phage

A

They are similar but the tail section is relatively longer in lambda phage

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

What is lambda phages’ life cycle?

A

Lyse the bacteria (lytic) or remain dormant inside the cell (lysogenic) . Bacteria will grown normally until irradiated with UV

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

Outline the Lytic cycle of lambda phage

A

Infection > Cell lysis

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

Outline the lysogenic cycle of lambda phae

A

Infection > Phage DNA cyclizes >

Decision point 1 > Phage DNA replicates > Progeny phages > Cell lysis

Decision point 2 > Integration of phage DNA > Cell division > UV induction > Phage DNA dissociates > Progeny phage > Cell lysis

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

How small are binding domains?

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

What regulatory proteins do lambda phage encode?

A

Cro and lambda-repressor (cl)

Cro is a repressor

cl is both activator and repressor

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

Outline structure of cl protein

A

C terminal is 132-236 amino acid residues
N Terminus is 1-92 amino acid residues

it forms a dimer via C-terminal domain

N terminal domain contacts DNA, each binding a major groove

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

Outline structure of cro proteins

A 
Forms dimers (homo-dimer)
Also binds DNA as a dimer

No N-terminal domains, thus no cooperative binding.

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

What is the significance of cro and cl proteins?

A

They both regulate the switch between the two states of bacteria, lytic and lysogenic state.

cl binds to OR1 and OR2
cro binds to OR3 only

OR is back to back promoters in Lambda bacteriophage.

cro and cl are transcribed in OPPOSITE directions

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

Which protein causes the lysogenic cycle?

A

cl protein, bound to OR1 and OR2

This helps RNA polymerase bind and more cI repressor is produced. cl repressor almost continously bound to OR1 and 2

cl repress cro synthesis

cl repressor binds with high affinity preventing access of RNA polymerase to cro promoter

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

Which protein causes the lytic cycle?

A

cri protein, bound to OR3, preventing access of RNA polymerase to left hand promoter (cl).

In absence of cl repressor, RNA polymerase binds to cro promoter.

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

How does the lysogenic cycle transition to the lytic cycle?

A

cl protein must be removed from OR1 to enable cro synthesis and binding to OR3. This can be caused by UV light.

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

How does UV cause stimulation of cro activity?

A

UV activates a bacterial protein, RecA, converting RecA to a protein digesting enzyme.

RecA cuts cl repressor, so it cannot form stable dimers

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

What is the function of cl protein?

A

Lysogeny

Binds to the cro promoter (OR1), preventing transcription of cro (negative control)

Binds to OR2, an activator. This enhances RNA polymerase binding to produce more new repressor protein.

Can bind to OR1,2 and 3 but affinity is highest for OR1

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

What is the function of cro protein?

A

Initiate lysis

Binds to OR3

Cro is only a REPRESSOR. It prevents binding of RNA polymerase to cl protein promoter so no mRNA is transcribed.

Can bind to OR1,2,3 but affinity is highest for OR3

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

What is the sequence binding length of both cl and cro?

A

15-20bp

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

How do proteins recognise their DNA binding site?

A

The base pairs expose their EDGES. These are NOT the groups involved in complementary base pairing along the central axis of the DNA double helix.

19
Q

What are palindromes?

A

2 fold symmetry.

OR1,2,3 sequences are similar but not identical. each are palindromic, specially at ends

20
Q

What are the similarities between cl and cro?

A

Both recognition helices begin Glutamine-Serine
Glutamine at #1 and serine at #2 contact DNA bases 2 and 4 respectively.

These 2 bases are invarient in all operator sites

so cl and cro use identical amino acids to contact identical bases in the operators

21
Q

Whats the difference between cl and cro?

A

Cro has asparagine at #5, which contacts position 3 in OR3
Cro has Lysine at #6, which contacts consecutive GG in OR3

cl has Alanine #6 which contacts T at OR1

cl and cro have the same helices orientation

22
Q

What determines if phage lambda should replicate or remain dormant?

A

If there is plenty of food, it will replicate. Otherwise it will remain dormant.

23
Q

What are the 3 stages to the phage gene expression following entry of phage DNA into bacteria?

A

Early
Delayed early
Late

Early and delayed early phases of gene expression occur before the decisions to switch to either lysogeny or the lytic phase.

In the late stage of gene expression, the switch operates.

Lytic cycle: early genes turned off. structural and lytic turned on.

Lysogenic: only 2 genes turned on,cl repressor and INT.
INT gene mediates the integration of the phae DNA into the bacterial chromosomes.

24
Q

What is lambda phages’ life cycle?

A

Lyse the bacteria (lytic) or remain dormant inside the cell (lysogenic) . Bacteria will grown normally until irradiated with UV

25
Q

Outline the Lytic cycle of lambda phage

A

Infection > Cell lysis

26
Q

Outline the lysogenic cycle of lambda phae

A

Infection > Phage DNA cyclizes >

Decision point 1 > Phage DNA replicates > Progeny phages > Cell lysis

Decision point 2 > Integration of phage DNA > Cell division > UV induction > Phage DNA dissociates > Progeny phage > Cell lysis

27
Q

How small are binding domains?

A

less than 100 amino acids

28
Q

What regulatory proteins do lambda phage encode?

A

Cro and lambda-repressor (cl)

Cro is a repressor

cl is both activator and repressor

29
Q

Outline structure of cl protein

A

C terminal is 132-236 amino acid residues
N Terminus is 1-92 amino acid residues

it forms a dimer via C-terminal domain

N terminal domain contacts DNA, each binding a major groove

30
Q

Outline structure of cro proteins

A 
Forms dimers (homo-dimer)
Also binds DNA as a dimer

No N-terminal domains, thus no cooperative binding.

31
Q

What is the significance of cro and cl proteins?

A

They both regulate the switch between the two states of bacteria, lytic and lysogenic state.

cl binds to OR1 and OR2
cro binds to OR3 only

OR is back to back promoters in Lambda bacteriophage.

cro and cl are transcribed in OPPOSITE directions

32
Q

Which protein causes the lysogenic cycle?

A

cl protein, bound to OR1 and OR2

This helps RNA polymerase bind and more cI repressor is produced. cl repressor almost continously bound to OR1 and 2

cl repress cro synthesis

cl repressor binds with high affinity preventing access of RNA polymerase to cro promoter

33
Q

Which protein causes the lytic cycle?

A

cri protein, bound to OR3, preventing access of RNA polymerase to left hand promoter (cl).

In absence of cl repressor, RNA polymerase binds to cro promoter.

34
Q

How does the lysogenic cycle transition to the lytic cycle?

A

cl protein must be removed from OR1 to enable cro synthesis and binding to OR3. This can be caused by UV light.

35
Q

How does UV cause stimulation of cro activity?

A

UV activates a bacterial protein, RecA, converting RecA to a protein digesting enzyme.

RecA cuts cl repressor, so it cannot form stable dimers

36
Q

What is the function of cl protein?

A

Lysogeny

Binds to the cro promoter (OR1), preventing transcription of cro (negative control)

Binds to OR2, an activator. This enhances RNA polymerase binding to produce more new repressor protein.

Can bind to OR1,2 and 3 but affinity is highest for OR1

37
Q

What is the function of cro protein?

A

Initiate lysis

Binds to OR3

Cro is only a REPRESSOR. It prevents binding of RNA polymerase to cl protein promoter so no mRNA is transcribed.

Can bind to OR1,2,3 but affinity is highest for OR3

38
Q

What is the sequence binding length of both cl and cro?

A

15-20bp

39
Q

How do proteins recognise their DNA binding site?

A

The base pairs expose their EDGES. These are NOT the groups involved in complementary base pairing along the central axis of the DNA double helix.

40
Q

What are palindromes?

A

2 fold symmetry.

OR1,2,3 sequences are similar but not identical. each are palindromic, specially at ends

41
Q

What are the similarities between cl and cro?

A

Both recognition helices begin Glutamine-Serine
Glutamine at #1 and serine at #2 contact DNA bases 2 and 4 respectively.

These 2 bases are invarient in all operator sites

so cl and cro use identical amino acids to contact identical bases in the operators

42
Q

Whats the difference between cl and cro?

A

Cro has asparagine at #5, which contacts position 3 in OR3
Cro has Lysine at #6, which contacts consecutive GG in OR3

cl has Alanine #6 which contacts T at OR1

cl and cro have the same helices orientation

43
Q

What determines if phage lambda should replicate or remain dormant?

A

If there is plenty of food, it will replicate. Otherwise it will remain dormant.

44
Q

What are the 3 stages to the phage gene expression following entry of phage DNA into bacteria?

A

Early
Delayed early
Late

Early and delayed early phases of gene expression occur before the decisions to switch to either lysogeny or the lytic phase.

In the late stage of gene expression, the switch operates.

Lytic cycle: early genes turned off. structural and lytic turned on.

Lysogenic: only 2 genes turned on,cl repressor and INT.
INT gene mediates the integration of the phae DNA into the bacterial chromosomes.

PM 228 - Gene expression (8 decks)

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