CBG22

Question 1

What are cells that support viral infection?

Answer 1

permissive

Question 2

What does a productive infection often lead to?

Answer 2

cytopathic effects

changes in cell

Question 3

What does infection of a non permissive cell lead to?

Answer 3

abortive or restrictive infection

Question 4

What is a persistent infection?

Answer 4

dont produce much

Question 5

What is a chronic infection?

Answer 5

low level over a long period of time

Question 6

What does a cytodical productive infection lead to?

Answer 6

death, releasese of infectious virus, morphological biochemical and physiological change and DNA degradation.

Question 7

What does a cytodical abortive infection lead to?

Answer 7

variable cell survival
no relase of virus
barable morphological, biochemical and physiological changes
maybe dna mutation

Question 8

What does a laten infection lead to?

Answer 8

survival, no changes

perhaps dna mutation

Question 9

What does chronic infectoiin lead to?

Answer 9

variablle affects
release of virus
variable morphological effects
dont strongly effect biochemistry or physiology
may cause mutations

Question 10

What do morphological effects include?

Answer 10

changes to nucleus (nuclear inclusion)
cytoskeleton
giant cell fromation

Question 11

How can a virus be diagnosed by looking at cytoskeleton?

example

Answer 11

by looking at affects on cytoskeleton
seen via light microscope
eg. nucelear and cytoplasmic inclusion in cell infected by cytomegalovirus

Question 12

What affect do measles and retroviruses have on cells that can be seen under the light microscope?

Answer 12

syncita produced by fusion of viral envelope with uninfected cells.

• virion entering cell causes production of viral fusion proteins
• causes cell to fuse more than one nucleus
• syncitial cell

Question 13

What are the effects of viruses on cell biochemistry and physiology?

Answer 13

1. activation of cellular proteins and kinases and transcription factors.
2. activation of cellular oncogenes, cell cycle arrest
3. inhibition of DNA synthesis

Question 14

What genetic effects can viruses have on host cells?

Answer 14

transformation , generalised chromosome damage.

Question 15

What happened to the viral syncitin gene?

Answer 15

stolen from viruses and domesticated in mammals
twice in primates
involved in placental formation

Question 16

What is the modern HIV medicine?

Answer 16

a combination of inhibitors

- as in interferon

Question 17

What is an example of an induced defence?

Answer 17

via interferon
-alpha and beta are the main antiviral defences in the body
interferon acts to induce viral state in cells ‘siege state’
from point of infection
stimulated by viral RNA

Question 18

What does interferon do?

Answer 18

as it is easy for virus to develop a mutation interferon activates a variety of inhibitors at the same time to target differetn stages of life cycle.

1. Transcription inhibitors. - block mrna synthesis
2. Translation inhibitors - block mrna, via cap and methylation- methylase, protein kinase, phosphodiesterase
3. protein processing inhibitor - blocks protein glycosylation
4. virus maturation inhibitors - blocks budding and glycoprotein maturation

Question 19

What can host defences to viruses be?

Answer 19

induced or non induced.
viral signals induce antibody defences to ready for infection
- not on all the time as slow down transcription/lation so inefficient

Question 20

What is TIP?

Answer 20

translation inhibitory protein
anti viral defence protein 
activated by interferon
once translated binds to ribosomes making it more particular about mRNA  it transaltes
only translates mrna with cap

Question 21

What mechanism does influenza have to overcome TIP?

Answer 21

cap snatching mechanism

not only increases viral translation but decreases host

Question 22

What is an example of a non induced defence?

Answer 22

APOBEC3G which defends against retroviruses.
enters viron and causes C->U G->A on coding strand- destroys virus
via hypermutation
- hits 30% of viruses that infect cells

Question 23

How does TRIM5 work?

Answer 23

act against uncoatinf of virus by binding to capsid protein- chimp
-TRIM5 blocks HIV in chimps
our TRIM5 blocks chimp RV

Question 24

What is RSV?

Answer 24

Rous Sarcoma Virus
Retrovirus
causes sarcoma in chickens
+ sense
src was taken up by RSV and incorperated into genome
src gene is an oncogene- stimualtes uncontrolled mitosis
src is non essential but increases its virulance

Question 25

What defence has HIV developed against APOBEC3G?

Answer 25

vif gene which binds to APOBEC3G and shunts it into degradation pathway.

Question 26

What did peyton do?

Answer 26

put chicken tumour extract into healthy chicken. tumour had virus. peyton isolated RSV
SRC gene produces tumours/proteins which make them

Question 27

What affect does papillomavirus have on cell?

Answer 27

causes cell transformation
= DNA virus
accidental transformation
not part of life cycle

Question 28

What is a benign growth/wart an example of?

Answer 28

accidental integration to host DNA of viral episome
causes unbalanced production of viral replication proteins
- causes malignant tumour
abortative - only half virus is reproduced

Question 29

What is an abortive infection?

Answer 29

Abortive infection, a viral infection that infects a cell without reproducing into more infectious viruses.

Question 30

What is a non permissive cell?

Answer 30

condition which does not support the replication of a mutant gene of a virus or bacteriophage