Viral properties L9

Question 1

3 shape variations of viruses

Answer 1

Icosahedral
filamentous
spherical

Question 2

icosahedral=

Answer 2

highly symmetric 20 faces

self-assembles

Question 3

3 significant features of viruses

Answer 3

1. Obligate intracellular parasite
2. Depend on biochemistry machinery of host cell to replicate
3. replication is by assembly of individual components

Question 4

what is the nucleocapsid

Answer 4

the genome contained within a protein capsule

Question 5

virion=

Answer 5

the infective viral particle

Question 6

for non-enveloped viruses (naked)=

Answer 6

nucleocapsid= virus particle= virion

Question 7

for enveloped viruses =

Answer 7

virion= nucleocapsid + envelope

Question 8

what often protrudes from the surface of the virus particle and are involved in contact with the host cell

Answer 8

protein or glycoprotein structures called spikes

Question 9

what can the enveloped be made from

Answer 9

derived from the host membrane via budding

Question 10

e.g of enveloped virus

Answer 10

influenza

Question 11

spikes on influenza (2)

Answer 11

• H

- N

Question 12

H spike=

Answer 12

hemagglutinin receptor recognition on host cell (specificity

Question 13

N spike=

Answer 13

neuramindase

Question 14

what are H and N susceptible to (2)

Answer 14

• antigenic drift (mutations)

- Shift (recombinations)

Question 15

e.g of a naked virus

Answer 15

norovirus

Question 16

3 advantages of being non-enveloped

Answer 16

1. more stable in face of environmental spread (no phospholipid membrane
2. spreads more easily
3. Survives gut, poor water treatment ect

Question 17

4 consequences about enveloped viruses

Answer 17

must stay wet to remain infectious
very sensitive to detergents
spreads through large droplets
does not need to kill cell to spread (buds)

Question 18

e.g 3 enveloped viruses

Answer 18

HIV
Ebola
Influenza

Question 19

what is the key way of classifying viruses

Answer 19

Nature of the genome

Question 20

transcription=

Answer 20

making a + strand mRNA from DNA

Question 21

what is negative mRNA

Answer 21

the complementary strand

Question 22

translation=

Answer 22

proteins from mRNA

always needs positive stranded mRNA

Question 23

2 tasks to make new virus particles

Answer 23

1. make mRNA to be translated to make new viral proteins

2. Make nucleic acids; copies of own genome to be packaged

Question 24

3 classes of protein viral genome codes for

Answer 24

1. proteins for progeny viral particles
2. Enzymes for genome replication
3. Proteins to interfere with host immune defence

Question 25

do humans have negative RNA

Answer 25

no

Question 26

3 classification of viruses on genome

Answer 26

RNA DNA retrovirus

Question 27

retrovirus=

Answer 27

contain reverse transcriptase | have RNA to DNA step in life cycle

Question 28

6 stages of the infectious cycle

Answer 28

- attachment - penetration - uncoating - replication (gene expression) - assembly - release

Question 29

burst size=

Answer 29

yield of infectious virus/cell | time required for single cell of virus to reproduce

Question 30

Negative ss RNA are all ______

Answer 30

enveloped

Question 31

entire life cycle is normally extra nuclear (3)

Answer 31

Negative ss RNA Positive ss RNA positive ds RNA

Question 32

in neg ss RNA how are progeny viruses released

Answer 32

budding

Question 33

life cycle of Retrovirus (e.g HIV)

Answer 33

- RT enzyme - viral genome integrates into host cell chromosomal DNA - viruses are packaged in cytoplasm and released by budding

Question 34

where are DNA viruses usually assembled

Answer 34

in the nucleus and released by cell lysis

Question 35

why very few antivirals?

Answer 35

limited choice of targets for anti-viral drugs

Question 36

what is it called when viral infection causes death of host cell

Answer 36

lytic infection

Question 37

what happens when genomic material is retained in host cells

Answer 37

latent infection

Question 38

slow release of viral particles may lead to

Answer 38

persistant infection

Question 39

how can viruses cause tumour cells

Answer 39

virus might induce transformation of the host cell leading to formation of normal cells to tumour cells

Question 40

what can be viral oncogenes (4)

Answer 40

regulatory factors receptor molecules for growth factors signalling molecules transcription factors

Question 41

2 ways oncogenes can occur

Answer 41

1. introduction of oncogenes | 2. insertion of viral DNA into host genome activates host cellular oncogenes

Question 42

shape of rotavirus

Answer 42

icosahedral

Question 43

shape of ebola

Answer 43

filamentous

Question 44

shape of adenovirus

Answer 44

spherical

Question 45

name 4 negative SS RNA viruses

Answer 45

influenza, mumps and measles rabies ebola

Question 46

name 3 positive SS/ds RNA viruses

Answer 46

poliovirus dengue hepatitis C

Question 47

name 2 DNA viruses

Answer 47

herpes, Epstein barr virus (EBV)

Question 48

name a retrovirus

Answer 48

HIV