L3 Virology

Question 1

what are viruses

Answer 1

obligate intracellular parasites

Question 2

what is the structure of a virus

Answer 2

nucleic acid surrounds by protein capsid (some also have lipid membrane - from host cell, acquire lipid membrane through one of the membranes in the eukaryotes e.g. cytoplasmic membrane)

Question 3

how do viruses enter cells

Answer 3

via interaction with specific cell receptors (lock and key) = TROPISM (which cells, tissues, organisms can the virus infect)

Question 4

how do viruses replicate when in host

Answer 4

host cell machinery is hijacked resulting in synthesis of new virus

Question 5

how are viruses released

Answer 5

by budding (enveloped viruses) or by cell lysis or via the secretory pathway

Question 6

what viruses dont result in a disease

Answer 6

orphan viruses

Question 7

what can viruses infect

Answer 7

bacteria
plants
animals
humans

Question 8

what is transmission electron microscopy

Answer 8

electrons pass through thin fixed specimen
electrons are blocked by it
electrons transmitted through specimen according to electron density

Question 9

what is scanning electron microscopy

Answer 9

specimen often immobilised and fixed on grid
electron interact with surface and back scattered also make x rays- both detected
gives surface topography

Question 10

what is scanning EM good for

Answer 10

viruses without lipid membrane (rigid structure)

Question 11

what is cryo-electron microscopy

Answer 11

specimen unfixed
immobilised by freezing to near zero temp
preserves native structural features
cyro-electron tomography uses 2D images to build 3D pic

Question 12

what is the effect of reducing the temp in cryo EM

Answer 12

reduce energy of virus so stop vibrating can see the virus

Question 13

what is a virion

Answer 13

virus particle

Question 14

what nucleic acid does a virus carry

Answer 14

RNA or DNA

Question 15

what nucleic acids do most viruses have

Answer 15

RNA

Question 16

what surrounds the virus

Answer 16

nucleic acid plus protein = nucleocapsid

Question 17

how are capsids arranged

Answer 17

in symmetrical patterns

most energetically favourable state

Question 18

what is the most favourable state for HIV

Answer 18

helical nucleocapsid with icosahedral core

Question 19

where do viruses get the lipid envelope

Answer 19

host cell membrane

Question 20

how viruses attach to cells

Answer 20

some of the virus proteins are involved in cell attachment and entry, (usually on the surface to allow virus to stick to cell they want to infect)

Question 21

what sort of enzymatic functions do viruses have

Answer 21

copying viral genome (polymerases)
trimming viral proteins (proteases)
other modifying enzymes

Question 22

what microscopy can see most viruses

Answer 22

electron

Question 23

what is the hierarchical classification system

Answer 23

grouped according to shared properties

• nucleic acid
• capsid symmetry
• presence/absence of envelope
• size
• ss/ds

Question 24

what is the family suffix

Answer 24

-viridae

Question 25

what is the genera suffix

Answer 25

-virus

Question 26

ICVT hierarchy of viral taxa

Answer 26

(order) > family > (sub-family) > genus > species

Question 27

what is baltimore classification

Answer 27

system based on replication strategy dictated by RNA or DNA genomes they contain 7 arbitrary groups

Question 28

what is group 1

Answer 28

dsDNA

Question 29

what do group 1 viruses do

Answer 29

dsDNA can replicate in nucleus (hijack your cells) or | cytoplasm and make their own enzymes for nucleic acid replication

Question 30

which group 1 viruses replicate in nucleus

Answer 30

adenovirus uses cellular proteins

Question 31

which group 1 viruses make own enzymes for nucleic acid replication

Answer 31

poxvirus

Question 32

what are the group 2 viruses

Answer 32

ssDNA

Question 33

what do group 2 viruses do

Answer 33

ssDNA replicate in nucleus | involve formation of (-) sense strand, serves as template for (+)strand RNA and DNA synthesis

Question 34

what are the group 3 viruses

Answer 34

dsRNA

Question 35

what are group 3 viruses like

Answer 35

dsRNA have segmented (usually each segment encodes one protein - monocistronic) or non-segmented linear genomes

Question 36

how do dsRNA viruses transcribe

Answer 36

most viruses with a segmented genome, each segment is transcribed separately to produce monocistronic mRNAs

Question 37

what are the group 4 viruses

Answer 37

(+) sense RNA viruses (enveloped) | +) sense RNA viruses (non-enveloped

Question 38

what do group 4 (+) sense RNA viruses (enveloped) do

Answer 38

mRNA naked RNA infectious - make new proteins which make new virus translation = formation of polyprotein product

Question 39

what are the group 4 (+) sense RNA viruses (non-enveloped)

Answer 39

- astrovirus - calicivirus - hepatitis a virus Picornaviridae

Question 40

why are group 4 viruses best to see under microscope

Answer 40

as non-enveloped

Question 41

what are the group 5 viruses

Answer 41

(-) sense RNA viruses (non-segmented enveloped) | -) sense RNA viruses (segmented enveloped

Question 42

what do group 5 (-) sense RNA viruses (non-segmented enveloped) have

Answer 42

have a virion particle RNA directed RNA polymerase

Question 43

what is the first stage of group 5 (-) sense RNA non segmented enveloped viruses

Answer 43

transcription by viral RdRp to produce monocistronic mRNAs

Question 44

why do group 5(-) sense RNA viruses (non-segmented enveloped) have their own RNA polymerase

Answer 44

need own RNA polymerase to make it positive strand as they are negative strand

Question 45

what are group 6 viruses

Answer 45

RNA reverse transcribing viruses

Question 46

example of group 6 viruses

Answer 46

retroviridae: HTLV-1, HIV

Question 47

what is the genome of group 6 viruses

Answer 47

(+)sense but unique among viruses in that it is DIPLOID (two copies of (+) strand RNA) serve as a template for reverse transcription to yield dsDNA

Question 48

what are the group 7 viruses

Answer 48

DNA reverse transcribing viruses

Question 49

example of group 7 viruses

Answer 49

hepadnaviridae - hepatitis B

Question 50

what do group 7 viruses need to make dsDNA

Answer 50

rely on reverse transcription from an RNA intermediate transcript to form partial dsDNA copy

Question 51

what happens first when group 7virus infects cell

Answer 51

repair of the gapped genome, followed by transcription

Question 52

what is the replication process of a virus

Answer 52

``` viral entry: receptor, tropism uncoating transcription and translation - viral proteins > structural, enzymatic and regulatory - viral genome production virus assembly virus release ```

Question 53

what changes to endosome as passes through cell

Answer 53

pH gets more acidic can hijack the cell

Question 54

what is needed for RNA virus replication

Answer 54

RNA dependent RNAse

Question 55

what do reverse transcribing viruses have/make - nucleic acids

Answer 55

RNA and DNA

Question 56

where can nucleocapsid assembly occur

Answer 56

nucleus or cytoplasm

Question 57

where do envelope viruses bud

Answer 57

cell membrane | sometimes golgi/ER

Question 58

where do non-envelope viruses mature

Answer 58

golgi/cytoplasm

Question 59

where are mature non-envelope viruses transported

Answer 59

secretary vesicles

Question 60

what happens when a (+) sense RNA viruses (non-enveloped) is introduced into cytoplasm

Answer 60

RNA in cytoplasm = virus

Question 61

what are group 5(-) sense RNA viruses (non-segmented enveloped)

Answer 61

- paramyxovirus (MMR) | - ebolavirus (filoviridae)

Question 62

where is the reverse transcription needed for group 7 DNA

Answer 62

inside maturing virus particle

Question 63

what are the group 4 (+) sense RNA (enveloped) viruses

Answer 63

coronavirus | togavirus

Question 64

what is the group 2 viruses

Answer 64

paroviridae

Question 65

what is the segmented dsRNA virus example

Answer 65

reoviridae

Question 66

what the the non-segmented dsRNA virus example

Answer 66

cystoviridae

Question 67

what are the group 5 (-) sense RNA (segmented enveloped) viruses

Answer 67

- arenaviridae - bunyaviridae - orthomyxoviridae