CBG Lecture 19: Bacterial Transduction Flashcards Preview

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Flashcards in CBG Lecture 19: Bacterial Transduction Deck (60):
1

define bacteriophage

a virus that infects bacteria

2

define lysogenic cycle

phage integrates into chromosome and is replicated along with the bacterial DNA

3

define lytic cyccle

the phage replicates in the host cell, releasing a new gen of viruses when the infected cell lyses

4

define virulent phage

reproduces only through lytic cycle
kills host

5

define prophage

a temperate bacteriophage integrated into the chromosome of the host bacterium

6

define temperate phage

can use lytic or lysogenic cycle

7

define plaque

a clear patch on bacterial lawn showing where cells have been lysed by phage infection

8

what two phages did Hershey and Rotman use

h-r+ and h+r-

9

wgucg E.coli strains can h- infect

E.coli strains B and B/2

10

which phage can infect E.coli B and B/2

h-

11

what happens when h- infects E.coli strains B and B/2

clear

12

which strain can h+ infect

strain B E.coli

13

what infects strain B E.coli

h+ and h=

14

what happens when h+ infects strain B

cloudy plaques

15

which infection gives clear plate

when h- infects E.coli strains B and B/2

16

which infection gives cloudy plaque

when h+ infects strain B

17

what does r- do

lyses cells rapidly giving large plaques

18

what does r+ do

lyses cells slowly giving small plaques

19

how are large plaques formed

by r- lysing cells rapidly

20

how are small plaques formed

by r+ lysing cells slowly

21

why do you cross h-r+ with h+r- in B strain bacteria

because this is the only strain which both phages can infect

22

why is high concn of phage used

to ensure multiple infections occur

23

when experimenting with phages, how do you ensure multiple infections occur

high concn of phage use

24

what is genotype of clear and small

h- r+

25

what is genotype of clear and large

h- r-

26

what is genotype of cloudy and small

h+ r+

27

what is genotype of cloudy and large

h+ r-

28

what is phenotype of h- r+

clear and small

29

what is phenotype of h+ r+

cloudy and small

30

what is phenotype of h+ r-

cloudy and large

31

what is phenotype of h-r-

clear and large

32

what causes triggering of lytic from lysogenic cycle

stressors
eg. UV - excises the phage DNA

33

what do plaques show

where cells have been lysed

34

what types of transduction are there

generalised
specific

35

what is generalised transduction

phages carry any part of the bacterial chromosomes

36

what can cotransduction be useful for

mapping genes (like cotransformation) - a headful of DNA is transferred at a time

37

what type of transduction where phages carry any part of the bact chromosome

generalised

38

what is specialisd transduction

phages carry only restricted parts of the bacterial chromosome

39

compare specialised transduction to generalized

in generalised phages carry ANY part of bact chrom and it involves the lytic cycle but in specialised transduction the lysogenic cycle is involved and specific genes are transferred - those next to phage attachment sites

40

give example of a phage used in specialised transduction

lamda phage

41

how can phages be excised from bact chrom

production of initial lysate then rare abnormal outlooping

42

which genes are transferred in specialised transduction

those next to phage attachment sites

43

what can transfer of genes be via

lysogenic incorporation into the bacterial chromosome or by recombination

44

what are the two ways that excision can appear

production of initial lysate
transduction by initial lysate

45

what is a bacterial lawn

the field of bacteria formed when all the individual colonies on a petri dish agar plate merge

46

what did hershey and rotman do

h-r+ and h+r- crossing to map phage genes

47

what did Lederberg and zinder do

can recombination occur in salmonella as it does in E.coli

48

what is production of initial lysate

produced via outlooping - involved in the excision of phage from bacterial chrom

49

what is transduction of initial lysate involved in

new genetic material in recipient cell

50

name some phages that show generalised transduction

p1 and p22

51

where does lamda phage insert betwen

specialised transducer which inserts between the gal and bio genes in the E.coli host chrom

52

how does lamda phage excise out of bact chrom

lamda phage is a specialised transducer and normally excises out of bact chrom via an outlooping mechanism that is precisely the reverse of its integration

53

when can lamda phage transduce

only when an occasional faulty outlooping includes the gal or bio genes into the phage cycle

54

what is a lysate

A popn of progeny phages

55

what is a known temperate phage of salmonella

P22 - it fits in the filter of U tube

56

what is zygotic induction

The sudden release of a lysogenic phage from an Hfr chromosome when the prophage enters the F− cell, and the subsequent lysis of the recipient cell.

57

how is the prophage attached to the bacterial genome

reciprocal recombination of lamda phage into E.coli chromsome = takes place between a specific attachement site of the circular lamda DNA and specific region on bac chrom between the gal and bio genes

58

what can specialised transduction prodeuce

normal labda, or abnormal lamda d gal - the transducing particle

59

when does transduction occur

when newly forming phages acquire host genes and transfer them to other bacterial cells

60

what is specialised transduction due to

faulty separation of the prophage from the bacterial chrom so the new phage includes both phage and bacterial genes = the transducing phage can transfer only specific host genes