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Genomics and Bioinformatics > Phage Lambda (λ) > Flashcards

Phage Lambda (λ) Flashcards

1
Q

name 2 physical features on the λ phage

A

-isocohedral head
-noncontractile tail

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2
Q

what is a bacteriophage?

A

viruses that infect bacteria

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3
Q

what repressor proteins are key?

A

-CL protein
-Cro proteins

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4
Q

what classification of bacteriophage is λphage?

A

ds DNA

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5
Q

name an example of ssRNA

A

leviviridae

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6
Q

cystoviridae is an example of what class of bacteriophage?

A

dsRNA

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7
Q

what is a lysogenic phage?

A

temperate phage

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8
Q

name 2 reproductive options

A

1-typically
2-lysogeny(remain within the host cell without destroying it)

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9
Q

describe a summary of the prophage stage in lysogeny

A

phage genome integrates on host bacterial genome- on chromosome for (λ) or plasmids for (P1).most phage genes not expressed. prophage reproduced in synchrony.

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10
Q

what is a lysogen

A

bacterial host infected w a prophage

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11
Q

what are host cell lysogens immune to?

A

superinfections by the same virus-phage repressor

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12
Q

decsribe the process of induction

A

under appropriate conditions, lysogen will lyse & release phage particles

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13
Q

what altered conditions can leave to induction?

A

host cell damage

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14
Q

what is a cryptic virus?

A

phage looses ability to leave the host via mutation

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15
Q

where does the integration of phage λ take place?

A

attachment site in the bacterial & phage genomes (att)

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16
Q

what happens on entry due to complementary base pairing in the lysogenic bacteriophage?

A

circularisation

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17
Q

att int xis -are all responsible for what stage in organisation of transcripts?

A

integration & excision

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18
Q

What’s responsible for recombination?

A

gam red

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19
Q

what does the control region include?

A

CIII N cI cro CII

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20
Q

O & P are responsible?

A

DNA replication

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21
Q

what is lysis controlled by?

A

S

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22
Q

Q is responsible for what stage?

A

late control

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23
Q

where is early transcription initiated?

A

P1 & P2

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24
Q

where is termination initated?

A

tL1 & tR1/tR2

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25
Q

what allows anti-termination & expression of delayed early genes?

A

The product of gene N & Q(from Pr)

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26
Q

tr3 is the site of what?

A

rightward transcript termination

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27
Q

what happens if CI wins the race with Cro?

A

transcription blocked for cro gene, N & Q.lysogeny is established.

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28
Q

what happens if Cro wins the race?

A

-Cro binds operating sites Or & OL, blocking transcription from the PR & PL
-Represses Pm & CII synthesis. Blocks OI synthesis
-prevents integration of the λ genome into the host chromosome

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29
Q

what triggers induction?

A

drop in levels of λ repressor(CI) caused by UV exposure

30
Q

What does Excisionase (Xis)

A

-binds integrase (int)
-enables integrase to reverse integration process

31
Q

what happens to the cohesive ends after infection?

A

theta θ mode-ligated together to form a circular molecule which replicates.

32
Q

rolling circle mode does what when switched over?

A

length linear DNA is generated, for further packaging into phage particles

33
Q

what is rolling circle replication required for?

A

production of the lytic cycle of replication-which generates multiple length linear DNA

34
Q

what is the replication forks’ role

A

proceeds around the template

35
Q

where is the nick of the primer located?

A

3’ -OH end

36
Q

why does temperate phage survive in a bacterium?

A

due to integration of their DNA into the host chromosome

37
Q

what can the temperate phage induce?

A

phenotype changes in the bacterium

38
Q

Escerichia coli O157:H7 saki strain description?

A

18 prophage genome,16% of entire genome

39
Q

what is a MORON?

A

after more DNA, phage often carries additional genes within elements(after more DNA)

40
Q

What impacts do MORONs have?

A

active players in cell physiology —->
become resistant to antibiotics,survive in other enviroments,produce toxins +other virulence factors

41
Q

where are morons identified?

A

within the prophage due to different G C content +own promoters & terminators

42
Q

resistance to quinolones & beta-lactams in E.coli mean what?

A

altered metabolic capabilities

43
Q

what allows E.coli to interact with & invade epithelial cells

A

phage λ protein

44
Q

what encodes survival of the host immune response-superoxide dimutase

A

gifsy-2 Salmonella prophage

45
Q

what protects against free radicals?

A

superoxide dimutase

46
Q

what protects E.coli from serum killing?

A

phage λ Bor protein

47
Q

exotoxins are involved with what?

A

bacterial pathogenicity

48
Q

give examples of defensive countermeasures bacteria use?

A

surface changes and restriction modifications

49
Q

helping defend ecological placing because…

A

phage are important led for acquisition of genes

50
Q

what does the decreased in fitness of lysogenic hosts mean?

A

metabolic burden to replicate extra DNA-lysis of the host after prophage induction

51
Q

what happens when prophage increase the fitness of lysogenic hosts?

A

immunity(phage repressor) & superinfection exclusion genes of prophage to protect lysogen

52
Q

give an extended description of the association of Lactobacillus delbruki

A

lytic phage rare, organism hard to transform with foreign DNA. strong barrier against intrusion of foreign DNA.

53
Q

what phage is readily detected in milk?

A

streptococcus thermophilis

54
Q

other features of streptococcus thermophilis include?

A

permissive to DNA transfer: few anti-phage mechanisms detected

55
Q

true or false
proteins secreted from bacteria that are toxic to eukaryotic cells?

A

true

56
Q

thick mucopurulent, nasal discharge, fever, sore throat, swollen cervical lymph- are all symptoms of what?

A

corneybacterium diphtheride

57
Q

diphtheria is encoded by what?

A

roxin β-phage

58
Q

give examples of systemic symptoms of diphtheria

A

destroys parenchyma of heart, liver, kidneys or adrenal glands

59
Q

genetic exchange in the enviroment-sewage/water treatments

A

phage stx 1+2, dtx and sea widespread

60
Q

what infects cats,cattle,pigs,horses?

A

transduction of stx between E.coli O157:H7 and commensal s.aureus

61
Q

what does the transduction of stx between E.coli O157:H7 and commensal s.aureus produce?

A

enterotoxins SEA.SEB,SEC

62
Q

what does ampliphi treat?

A

pseudomonas aureginosa, cystic fibrosis, MRSA, infections of burns

63
Q

name the different serotypes of cholera

A

ISS, OI-el Tor, O139:bengal strain

64
Q

give the line knock on affect of the ingestion of V.cholera

A

adheres to colonies on small intestine ->
CTX acts on mucosal cells(diarrhoea)

65
Q

whats encoded on a single gene locus regarding cholera?

A

incomplete enome of a filamentous bacreiophage CTX

66
Q

what does the CTX phage lack?

A

secretin but uses the host secretin encoded by type II secretion apparatus

67
Q

what integrated filamentous bacteriophage genome carries the cholera toxin gene?

A

CTX Φ on chromosome 1

68
Q

what does TCP stand for?

A

toxin co-regulated pilus

69
Q

what is TCP a receptor for?

A

phage CTX Ψ

70
Q
A

Genomics and Bioinformatics (4 decks)

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