Lecture 9

Question 1

T7: podoviridae

Answer 1

-thicc
-naked icosahedral capsid
-60nm
-shirt tail and tail fibers
-lytic no lysogeny
-linear dsdna genome 40kbp
-phage receptor: LPS

Question 2

true or false: the Ty genome is divided in clusters

Answer 2

true in 3
-class I : early
-class II: dna metabolism
-class III: virion structure and assembly

Question 3

entry of T7 DNA into cytoplasm

Answer 3

-attached to the surface of the bacterial cell wall
-introduces its phage DNA in bacteria by making a tunnel through the OM, PG and IM
-e.coli rna pol binds to promoter sequence of the phage RNA
-class I genes are expressed

Question 4

what are the 3 special genes in T7 and what do they do

Answer 4

Gene 0.3: inhibits host type I restriction endonucleases
Gene 0.7: inhibits E coli RNA Pol
Gene 1: T7 RNA Pol

Question 5

true or false: T7 carries its own polymerase

Answer 5

true

Question 6

True or false: the DNA ligase in T7 is a class I gene

Answer 6

false: it is a class II gene

Question 7

what are the 4 class III gene in T7

Answer 7

8: portal protein
9: scaffolding protein
10: capsid protein
11: tail protein

Question 8

T7 RNA pol

Answer 8

-e.coli rna pol canm only transcribe genes from class I promoters not II and III
-dna entry proceeds until class II promoters are reached
-T7 rna pol encoded in Class I genes
-takes over from e.coli rna pol in transporting DNA into cell

Question 9

explain t7 dna replication

Answer 9

oop

Question 10

why do the T7 phage makes concameter

Answer 10

problem:
-dna pol needs a primer to initiate DNA synthesis
-thus the rna primer at the 3’ end of template DNA cannot be removed or replaced with dna=loss in sequence

Question 11

is T7 dna replication unidirectional or bi

Answer 11

bidirectional

Question 12

true or false t7 dna replication looks like ecoli DNA synthesis

Answer 12

true
continuous leading and lagging strands

Question 13

true or falseL t7 encodes all its own DNA replication proteins

Answer 13

true

Question 14

how are the large concameters of t7 made

Answer 14

formed via 150 bp terminal repeats

Question 15

t7 phage life replication

Answer 15

ppt 14 lect 9

Question 16

lambda phage

Answer 16

-siphoviridae
-dsdna
-ssdna at the ends aka cohesive ends
-temperate bacteriophage
-icosahedral dead
-tube like tail non-contractile
-receptor- surgar transport proteins lamB (maltose transporter_
-used to construct the cDNA libraries

Question 17

what are temperate phages:

Answer 17

able to gropw lytically or exist as a repressed prophage

Question 18

prophage

Answer 18

integrated phage dna, lytic genes are repressed, passivally replicate with host chromosome

Question 19

lysogen

Answer 19

bacteria carrying prophage

Question 20

explain the whole genome of lambda

Answer 20

oop

Question 21

how does lambda regulate transcriotion

Answer 21

-transcription start: activator and repressor
termination: antiterminator

Question 22

explain initial transcription events

Answer 22

oop
ppt 20 lec 9 -24

Question 23

true or false: CII initiates the establishment of lysogenic phage of infection

Answer 23

true
Cll is inactivated by a host cell protease, has a very short half-life (a few minutes), its stability is enhanced by Clll whose expression is driven by PL and can inactivate host cell proteases. Cll itself is much less stable in metabolically
active cells. go see ptt 25 lect 9

Question 24

go lytic or lysogenic?

Answer 24

-Upon infecting a bacterium, N and Cro are expressed
-Cro suppresses the expression of CI from PRM
-N leads to the expression of early genes CII and CIII
-In metabolic active cells, CII is very unstable, unable to
activate CI expression from PRE, GO LYTIC
-In metabolic inactive cells, CII is more stable, reaches high enough concentration to activate CI expression from PRE, GO LYSOGENIC

Question 25

retroregulation of int expression

Answer 25

see ppt 27 lec 9

Question 26

what does the lambda phage need to integrate the DNA and yeet away?

Answer 26

-integrate: INT, IHF
-yeet: int, IHF, Xis

Question 27

The great escape aka temperate phages-> lytic

Answer 27

-Stresses such as ultraviolet light irradiation causes DNA damage that activates RecA protein which in turn binds
to CI, stimulates the autoprotease activity of CI and leads to CI cleavage.
-Transcription from the PL promoter leads to the production of mRNA that direct the synthesis of both Xis and Int that together with IHF excise and liberate prophage DNA.

Question 28

cdna

Answer 28

basically you use a replacable region in a phage, you digest it and you digest human DNA and you mix them, now you get a recombinant virion containing genomic DNA