CBG Lecture 19: Bacterial Transduction

Question 1

define bacteriophage

Answer 1

a virus that infects bacteria

Question 2

define lysogenic cycle

Answer 2

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

Question 3

define lytic cyccle

Answer 3

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

Question 4

define virulent phage

Answer 4

reproduces only through lytic cycle

kills host

Question 5

define prophage

Answer 5

a temperate bacteriophage integrated into the chromosome of the host bacterium

Question 6

define temperate phage

Answer 6

can use lytic or lysogenic cycle

Question 7

define plaque

Answer 7

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

Question 8

what two phages did Hershey and Rotman use

Answer 8

h-r+ and h+r-

Question 9

wgucg E.coli strains can h- infect

Answer 9

E.coli strains B and B/2

Question 10

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

Answer 10

h-

Question 11

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

Answer 11

clear

Question 12

which strain can h+ infect

Answer 12

strain B E.coli

Question 13

what infects strain B E.coli

Answer 13

h+ and h=

Question 14

what happens when h+ infects strain B

Answer 14

cloudy plaques

Question 15

which infection gives clear plate

Answer 15

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

Question 16

which infection gives cloudy plaque

Answer 16

when h+ infects strain B

Question 17

what does r- do

Answer 17

lyses cells rapidly giving large plaques

Question 18

what does r+ do

Answer 18

lyses cells slowly giving small plaques

Question 19

how are large plaques formed

Answer 19

by r- lysing cells rapidly

Question 20

how are small plaques formed

Answer 20

by r+ lysing cells slowly

Question 21

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

Answer 21

because this is the only strain which both phages can infect

Question 22

why is high concn of phage used

Answer 22

to ensure multiple infections occur

Question 23

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

Answer 23

high concn of phage use

Question 24

what is genotype of clear and small

Answer 24

h- r+

Question 25

what is genotype of clear and large

Answer 25

h- r-

Question 26

what is genotype of cloudy and small

Answer 26

h+ r+

Question 27

what is genotype of cloudy and large

Answer 27

h+ r-

Question 28

what is phenotype of h- r+

Answer 28

clear and small

Question 29

what is phenotype of h+ r+

Answer 29

cloudy and small

Question 30

what is phenotype of h+ r-

Answer 30

cloudy and large

Question 31

what is phenotype of h-r-

Answer 31

clear and large

Question 32

what causes triggering of lytic from lysogenic cycle

Answer 32

stressors | eg. UV - excises the phage DNA

Question 33

what do plaques show

Answer 33

where cells have been lysed

Question 34

what types of transduction are there

Answer 34

generalised | specific

Question 35

what is generalised transduction

Answer 35

phages carry any part of the bacterial chromosomes

Question 36

what can cotransduction be useful for

Answer 36

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

Question 37

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

Answer 37

generalised

Question 38

what is specialisd transduction

Answer 38

phages carry only restricted parts of the bacterial chromosome

Question 39

compare specialised transduction to generalized

Answer 39

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

Question 40

give example of a phage used in specialised transduction

Answer 40

lamda phage

Question 41

how can phages be excised from bact chrom

Answer 41

production of initial lysate then rare abnormal outlooping

Question 42

which genes are transferred in specialised transduction

Answer 42

those next to phage attachment sites

Question 43

what can transfer of genes be via

Answer 43

lysogenic incorporation into the bacterial chromosome or by recombination

Question 44

what are the two ways that excision can appear

Answer 44

production of initial lysate | transduction by initial lysate

Question 45

what is a bacterial lawn

Answer 45

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

Question 46

what did hershey and rotman do

Answer 46

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

Question 47

what did Lederberg and zinder do

Answer 47

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

Question 48

what is production of initial lysate

Answer 48

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

Question 49

what is transduction of initial lysate involved in

Answer 49

new genetic material in recipient cell

Question 50

name some phages that show generalised transduction

Answer 50

p1 and p22

Question 51

where does lamda phage insert betwen

Answer 51

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

Question 52

how does lamda phage excise out of bact chrom

Answer 52

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

Question 53

when can lamda phage transduce

Answer 53

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

Question 54

what is a lysate

Answer 54

A popn of progeny phages

Question 55

what is a known temperate phage of salmonella

Answer 55

P22 - it fits in the filter of U tube

Question 56

what is zygotic induction

Answer 56

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.

Question 57

how is the prophage attached to the bacterial genome

Answer 57

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

Question 58

what can specialised transduction prodeuce

Answer 58

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

Question 59

when does transduction occur

Answer 59

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

Question 60

what is specialised transduction due to

Answer 60

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