Block D 3

Question 1

virus

Answer 1

genetic element that cannot replicate independently of a living (host)

Question 2

virology

Answer 2

study of viruses

Question 3

virus particle (virion)

Answer 3

extracellular form of a virus

Question 4

what does a virion contain

Answer 4

nucleic acid genome surrounded by a protein coat (capsid) and in some cases other layers of material

Question 5

4 phases of the viral replication attachment (adsorption) of the virus to host cell

Answer 5

-entry (penetration) of virion or nucleic acid
-synthesis of virus nucleic acid and protein
-assembly of capsids and packing of viral genomes
-release of mature virions from host

Question 6

what type of curve is virus replication typically characterised by

Answer 6

one step growth curve

Question 7

what is the latent period of virus life cycle

Answer 7

eclipse and maturation

Question 8

what is burst size of virus life cycle

Answer 8

number of virions released

Question 9

how is quantification of bacterial virus carried out

Answer 9

plaque assay

Question 10

what do the best studied bacteriophages infect

Answer 10

enteric bacteria

Question 11

what do most phages contain

Answer 11

dsDNA genomes

Question 12

most bacteriophages are naked but what do some possess

Answer 12

lipid envelopes

Question 13

what do most viruses that infect archaea resemble

Answer 13

those that infect enteric bacteria

Question 14

how many infections are initiated per second

Answer 14

10^25

Question 15

10^14 g phages on earth is approx. the same total mass of what

Answer 15

homo sapiens (50kg per person)

Question 16

attachment of virion to host cell is said to be what

Answer 16

highly specific

Question 17

attachment and entry of bacteriophage T4 requires complementary receptors on what

Answer 17

the surface of susceptible host and its infecting virus

Question 18

what do receptors on host cell carry out for cell

Answer 18

normal functions (eg uptake proteins, cell to cell interactions)

Question 19

what do the receptors include (in attachment and entry of bacteriophage T4)

Answer 19

proteins
carbohydrates
glycoproteins
lipids
lipoproteins
complexes

Question 20

what does the attachment of a virus to its host cell result in

Answer 20

changes to both virus and cell surface that facilitate penetration

Question 21

what is a permissive cell

Answer 21

host cell that allows the complete replication cycle of a virus to occur

Question 22

what is bacteriophage T4

Answer 22

virus of E.coli
one of the most complex penetration mechanisms

Question 23

in the attachment of bacteriophage T4 virions attach to cells via what

Answer 23

tail fibres

Question 24

what do the tail fibres that attach virions to cells interact with

Answer 24

polysaccharides on E.coli cell envelope

Question 25

in attachment of bacteriophage T4 the tail fibres then contract, what does the tail coremake contact with

Answer 25

E.coli cell wall

Question 26

what do the lysozyme like enzyme form in attachment and entry of bacterio. T4

Answer 26

small pore in peptidoglycan

Question 27

once the tail sheath has contracted what happens with the viral DNA in attachment and entry of bacterio. T4

Answer 27

viral DNA passes into the cytoplasm

Question 28

what type of genome does T4 have

Answer 28

dsDNA

Question 29

T4 a genome that is said to be what

Answer 29

circularly permuted and terminally redundant

Question 30

what is restriction modification system and what is it only effective against

Answer 30

DNA destruction system only against double stranded DNA viruses

Question 31

example of restriction enzyme

Answer 31

restriction endonuclease

Question 32

what do restriction enzymes do

Answer 32

cleave DNA at specific sequences

Question 33

what does modification of hosts own DNA at restriction enzyme recognition sites prevent

Answer 33

cleavage of own DNA

Question 34

what are the 3 viral mechanisms to evade bacterial restriction systems

Answer 34

-chem modif. of viral DNA (glycosylation or methylation) -production of proteins that inhibit host cell restriction system -T4 containing a modified base

Question 35

what is the name of the modified base that T4 has that helps evade bacterial restriction systems

Answer 35

5-hydroxymethylcytosine its DNA is resistant to virtually all known restriction enzymes

Question 36

what are the 3 parts that the T4 genome can be divided into

Answer 36

early middle late proteins

Question 37

what stages are the enzymes needed for DNA rep and transcription (replication of bacteriophage T4)

Answer 37

early and middle proteins

Question 38

what are late proteins

Answer 38

head and tail proteins and enzymes req to liberate mature phage particles

Question 39

what stage of proteins are needed for the synthesis and glucosylation of hydromethylcytosine

Answer 39

early proteins

Question 40

what stage of proteins are needed for enzymes that function of T4 replisome

Answer 40

early proteins

Question 41

what stage of proteins are needed for proteins that modify host RNA pol

Answer 41

early proteins

Question 42

what stage of proteins are needed for additional proteins that modify host RNA pol

Answer 42

middle proteins

Question 43

what stage of proteins are needed for production of viral proteins

Answer 43

middle proteins

Question 44

what stage of proteins are synthesised later

Answer 44

late proteins

Question 45

what stage of proteins include proteins of virus coat

Answer 45

late proteins

Question 46

what stage of proteins are synthesised in larger amounts

Answer 46

late proteins

Question 47

in the packaging of the T4 genome double stranded DNA is pumped into head under pressure using what

Answer 47

ATP

Question 48

in packaging of T4 genome after head is filled with DNA what other components are added

Answer 48

T4 tail tail fibres + more

Question 49

virulent mode

Answer 49

viruses lyse host cells after infection

Question 50

temperate mode

Answer 50

viruses replicate their genomes in tandem with host genome and without killing host

Question 51

temperate viruses

Answer 51

can undergo a stable genetic relationship within the host (but can also kill cells through lytic cycle)

Question 52

lysogeny

Answer 52

state where most virus genes are not expressed and virus genome (prophage) is replicated in synrony with host chr.

Question 53

lysogen

Answer 53

a bacterium containing a prophage

Question 54

what is the genome of bacteriophage lambda

Answer 54

linear dsDNA

Question 55

what is bacteriophage lambda

Answer 55

complementary single stranded 12 nucleotides long at the 5' terminus of each strand

Question 56

what forms upon penetration of bacterio. lambda

Answer 56

the cos site

Question 57

what occurs once cos site has been formed

Answer 57

DNA ligates and forms double stranded circle

Question 58

when lambda is lysogenic what happens to its DNA

Answer 58

integrates into E.coli chr at lamba attachment site (attλ)

Question 59

what occurs when bac. λ enters lytic pathway

Answer 59

λ synthesises long linear concatemers of DNA by rolling circle replication

Question 60

what is the regulation of lytic vs lysogenic events in λ controlled by

Answer 60

complex genetic switch 2 repressor proteins

Question 61

what repressor proteins causes repression of λ lytic events (activates lysogeny)

Answer 61

cl protein (the λ repressor)

Question 62

what repressor protein controls activation of lytic events (represses lysogenic genes)

Answer 62

cro repressor

Question 63

what is the key to the balance of the 2 repressor protein in the cell

Answer 63

the physiology of the bacterial host

Question 64

what drives bacterial evolution

Answer 64

transfer of DNA from one cell to another by a bacteriophage due to mispacking of the bacteriophage genome

Question 65

what are the names of the 2 modes of transduction

Answer 65

generalised transduction specialised transduction

Question 66

generalised transduction

Answer 66

DNA from any portion of the host genome is packaged inside the virion