test four lec 19

Question 1

what are acute viruses

Answer 1

kill their host

Question 2

what happens in lysogenic cycle

Answer 2

bacteriophage is quiescent
integrates into cell chromosome as prophage
can reactivate to become lytic
transduction

Question 3

what are prions

Answer 3

proteins that infect animals

Question 4

what is a viral capsid composed of

Answer 4

repeated protein subunits

maximizes capacity while minimizing the required number of genes

Question 5

how does slow release work

Answer 5

filamentous phages can extrude individual progeny through cell envelope
host cells grow slowly but dont die
use SS DNA to create DS DNA and reproduce

Question 6

what makes ocean viruses different

Answer 6

most numerous and genetically diverse forms of life

control algae bloom

Question 7

viral ecologists believe what of viruses

Answer 7

living entities

predator or parasite

Question 8

how are animal viruses cultured

Answer 8

within whole animals by serial inoculation
ensures virus maintains its original virulence
can also grow in human cell tissue culture

Question 9

what is the function of a capsid

Answer 9

packages the viral genome and delivers it into the host cell

they vary based on virus

Question 10

what are the seven fundamental groups of viral species by baltimore virus classification

Answer 10

DS DNA
SS DNA
DS RNA
\+ SS RNA
- SS RNA
RNA retrovirus
DNA pararetrovirus

Question 11

what dictates wether lytic or lysogenic

Answer 11

environmental cues

threaten host cell survival

Question 12

what type of defenses have bacteria created against bacteriophage infection

Answer 12

genetic resistance
(alter receptor proteins)
restriction endonucleases
CRISPR
(integration of phage DNA sequences)
bacterial immune system

Question 13

how can you measure relatedness of different viruses of a common ancestor

Answer 13

comparing their genome sequence

Question 14

what is a virus

Answer 14

a non cellular particle that must infect a host cell, where it reproduces

Question 15

what is used to reveal common descent of viruses with shared infected hosts

Answer 15

statistical analysis

Question 16

what are viroids

Answer 16

RNA molecules that infect plants

Question 17

what allows viruses to attach to host cells

Answer 17

cell surface receptors

Question 18

what is the baltimore virus classification

Answer 18

primary distinction among classes of viruses is genome composition and the route used to express messenger RNA

Question 19

how are viral genomes classified

Answer 19

baltimore method
viral proteins
capsid
envelope proteins
polymerase

Question 20

how does lysis work

Answer 20

make enzyme that breaks down cell wall

host cell bursts to release progeny phage

Question 21

what type of curve do batch cultures of viruses create

Answer 21

step curve

Question 22

what is the envelope like in an icosahedral virus

Answer 22

contains glycoprotein spikes

teguments are present inbetween the envelope and capsid

Question 23

what is a virion

Answer 23

a virus particle

Question 24

do viruses play a significant role in carbon balance

Answer 24

yes

Question 25

when do you use proteomic classification

Answer 25

useful of viruses because their small genomes encode few proteins

Question 26

how do viruses fill important niches in all ecosystems

Answer 26

limiting host population density | selecting for host diveristy

Question 27

what type of genome do large viruses have

Answer 27

more than 100 genes

Question 28

what are bacterial cell receptors used for

Answer 28

sugar uptake (maltose)

Question 29

how does a new virus emerge to sicken humans

Answer 29

humans eat wildlife (SARS) as variants of endemic milder pathogen (H7N9)

Question 30

what environment can you find viruses

Answer 30

all types

Question 31

what are the characteristics of a filamentous virus

Answer 31

``` capsid consists of a long tube of protein genome coiled inside vary in length (genome size) include bacteriophage and animal viruses helical symmetry (tube around genome) usually contain ss DNA and RNA ```

Question 32

what type of organism does viruses infect

Answer 32

all types

Question 33

what are cell surface receptors

Answer 33

proteins that are specific to the host species and which bind to a specific viral component

Question 34

what are the two types of life cycles of bacteriophages

Answer 34

lytic | lysogenic

Question 35

how do viruses infect hosts

Answer 35

mimicking by spreading "computer viruses" whose info "infects" computer memory

Question 36

the pox virus has what type of capsid

Answer 36

genome surrounded by several layers (core envelope with outermembrane) contain large number of accessory proteins

Question 37

how do you culture viruses

Answer 37

requires growth in host cell | bacteriophages cultured either in batch culture or as isolate plaques on a bacterial lawn

Question 38

how do viroids replicates

Answer 38

they use the host RNA polymerase

Question 39

what are the characteristics of icosahedral viruses

Answer 39

polyhedral 20 identical triangular faces rational symmetry capsid is enclosed in an envelope

Question 40

acute vs persistant viruses

Answer 40

acute outnumbers in natural ecosystems

Question 41

what are orthologs

Answer 41

genes of common ancestry in two genomes that share the same function

Question 42

what is the criteria that is used by the ICTV over virus taxonomy

Answer 42

``` genomes composition capsid symmetry envelope size of the virion host range ```

Question 43

what are the two types of symmetrical viruses

Answer 43

icosahedral and filamentous

Question 44

what are the two types of capsids

Answer 44

symmetrical and asymmetrical

Question 45

what happens in the lytic cycle

Answer 45

bacteriophage quickly replicates killing host cell | cause cell to burst, releasing new phages

Question 46

what type of genome do small viruses have

Answer 46

small | encoding under 10 genes, which may overlap in sequence

Question 47

what does a virion consist of

Answer 47

a single nucleic acid (DNA or RNA) contained within a protective protein capsid

Question 48

what are persistant viruses

Answer 48

along for the ride | may evolve traits that confer positive benefits in a virus-host mutualsim

Question 49

what is needed for host infection

Answer 49

host recognition and attachment genome entry assembly of virions exit and transmission

Question 50

what is transduction

Answer 50

take host genome and pass it on to other cells

Question 51

how do most viruses interact with hosts

Answer 51

positively | express host genes and by protecting hosts from other organisms

Question 52

what characteristic does T4 bacteriophages have with asymmetrical

Answer 52

have icosahedral head and helical neck

Question 53

what are proteoms

Answer 53

proteins encoded by genomes

Question 54

what is injected from phages into host cell

Answer 54

only genome through cell envelope phage capsid remain outside "ghost"

Question 55

characteristic of asymmetrical viruses

Answer 55

complex multipart structures

Question 56

what is required for viruses to replicate

Answer 56

require host cell

Question 57

do viroids have protein capsids

Answer 57

no

Question 58

what makes prions different

Answer 58

they have NO nucleic acid component | have abnormal structure that alters the conformation of other normal proteins

Question 59

what type of genome comparison is used when finding common ancestor

Answer 59

orthologs