MT3 Session 13: Bacteriophages

Question 1

T-even bacteriphage parts

type of DNA/RNA

Answer 1

capsid, tail=sheath+tube, 2 sets of 6 tail fibers, baseplate

linear dsDNA

Question 2

T-even bacteriophage attachment

Answer 2

to LPS, porin OmpC

Question 3

entry mech of T4

Answer 3

tail fiber bind, baseplate binding induces sheath contraction, cell wall degrade, pressure pushes DNA in

Question 4

virus life cycle necessities

Answer 4

1. attach to host cell - use host receptor
2. genome entry
3. virion assembly
4. exit

Question 5

burst size

Answer 5

#virus/ particle that burst
=#virus after 1st rep/#virus originally

Question 6

“early genes”

Answer 6

for DNA rep, regulate/lack of

Question 7

“late genes”

Answer 7

for lysis

Question 8

mech that temperate phages use to incorporate into host DNA

Answer 8

site specific recombo

Question 9

name of phages that:
undergo lytic cycle
undergo lytic AND lysogenic

Answer 9

virulent, temperate

Question 10

early gene fxns of T4 include

Answer 10

cleave host DNA, replace key host enzymes

Question 11

replication method of T4 - mech list

Answer 11

rolling circle :

1. linear circularizes
2. nick
3. detach + replace
4. fll and cut

Question 12

Lytic cycle steps

Answer 12

1. attachment and inject
2. early genes transcribed
3. rolling circle rep
4. late genes make head and tail
5. package heads
6. add tail
7. add tail fibers
8. pop!

Question 13

late genes of T4 include

Answer 13

making capsid, tail

Question 14

eclipse period

Answer 14

after adding cells, when [virus]=0, before rep

Question 15

latent period

Answer 15

eclpse period + replication, haven’tpopped

Question 16

rise period

Answer 16

when lysis releases until constant concentration of viruses - ALL FREED

Question 17

lysate

Answer 17

end pt suspension of particles
proportional to burst size x cell density :
  (#v  )(#cells)
 \_\_\_\_\_\_\_\_\_\_\_\_
  (cell)(vial)

Question 18

plaque assay steps

Answer 18

add phage to bacteria, to agar

pour on plate -> see plaque

Question 19

how do you find out the sequential steps of viral assembly?

Answer 19

use defectives with conditional lethal mutation:
abnormal features, stopped progress
temp sensitive, nonsense mutations+nonsense supressor tRNA

Question 20

T4 mutant gne 19

Answer 20

won’t create internal tube onto baseplate

so see only baseplates

Question 21

concatemer

Answer 21

long DNA line - repeat a chromosomal unit mult times

Question 22

terminal redundancy of T4

Answer 22

has 3% more of normal chromosome length - @ beginning repeated at end

Question 23

bacteriophage λ

morphology

Answer 23

icosa head, tail, no tail fiber

Question 24

bacteriophage λ

receptor

Answer 24

LamB = maltoporin - for maltodextrin (starch degrade prod - xglucose lines

Question 25

how do you get more bacteriophage λ’s to infect a single cell?

Answer 25

add maltose

cells will make more maltoporins –> more entry sites

Question 26

what does T4 infect?

Answer 26

E coli

Question 27

what does bacteriophage λ infect?

Answer 27

E coli

Question 28

what does bacteriophage P22 infect??

Answer 28

S. enterica

Question 29

lysogen

Answer 29

resultant host in lysogeny after viral dna is incorporated

Question 30

name of phage in quiescent state

Answer 30

prophage

Question 31

bacteriophage λ: virulent? temperate?

Answer 31

temperate

Question 32

lysogeny

Answer 32

incorporation into hst DNA

Question 33

name of cause for prophage exiting the host DNA

Answer 33

induction

Question 34

lysogeny rep:

Answer 34

theta replication - bidirectional + site spec recombo

Question 35

gene regulation for lysis/lysogeny

both have ___

Answer 35

both have early genes at some point

lysis: early off, late on
lysogeny: lysis off (early, late), integration on

Question 36

bacteriophage λ late genes

REGULATION

Answer 36

N (early) allows Q(late): there’s a cascade before committing
temporal so all steps are completed in order before proceeding

Question 37

bacteriophage λ encapsulation mechanism

Answer 37

still has concatemeric DNA

TERMINASE cuts dna at COS (cohesive site) site with sticky ends for RECIRCULARIZING

Question 38

bacteriophage λ LYSOGENY INTEGRATION
protein
mech

Answer 38

• RECOMBINASE to recog host sites &no RecA
  site specific recombo:
  -chromosome attW.w split in half, λ attXx site cut in half by INTEGRASE –> forms Wx, wX
• need EXISIONASE to cut it back out because the attachment sites are no longer the same

Question 39

attP, attB, att_

Answer 39

attachment site in bacteriophage λ for site specific recombo

Question 40

why do you need exisionase in bacteriophage λ?

Answer 40

site specific recombo creates two recominant attachment sites, so integrase can’t catalize the back reaction because it can’t bind

Question 41

bacteriophage λ repression

Answer 41

c1

Question 42

bacteriophage λ derepression

Answer 42

RecA starts induction of prophage: causes cleaves LexA ,

Question 43

LexA

Answer 43

represses synthesis of DNA -supresses SOS system

Question 44

why is RecA a good induction starter for bacteriophage λ?

Answer 44

it cuts out the prophage when it detects DNA damage

-> indicates host is compromised–>

Question 45

aberrant recombination

Answer 45

improper excision allows bacteriophage genes to be left in host, and phage carries host genes (likeshiga toxin)

Question 46

how does Phave P22 encapsulate?

Answer 46

cuts when head is filled up “headful encapsulation”

Question 47

what phage often does generalized transduction (swaps its carrier DNA for the host’s)

Answer 47

P22

Question 48

M13 life cycle

Answer 48

slow release- don’t lyse host cell

1. insert circular ssDNA -> dsDNA
2. replicate circular ssDNA, assemble
3. have phages bud out as the cell grows (at slower rate)

Question 49

colored bacteriophage plaques o f M13

Answer 49

b galactosidase or not (white)