2- viruses Flashcards
1
Q
lambda bacteriophage
A
- icosahedral capsid
- DNA
- infects E. coli
2
Q
draw lambda bacteriophage
A
3
Q
tobacco mosaic virus (TMV)
A
- helical capsid
- positive-sense ssRNA
- infects tobacco plants
4
Q
draw tobacco mosaic virus (TMV)
A
5
Q
ebola
A
- helical capsid with a lipid envelope
- negative-sense ssRNA
- infects human cells
6
Q
draw ebola
A
7
Q
HIV
A
- enveloped icosahedral capsid
- ssRNA retrovirus
- infects T cells
- enzymes include reverse transcriptase
8
Q
DNA viruses
A
- viral DNA is replicated using the host cells replication machinery
- the replicated DNA is transcribed into mRNA, which is translated into proteins by the host cell
- the newly formed proteins and viral DNA assemble into new viral particles
9
Q
RNA viruses- positive sense ssRNA
A
- positive RNA is translated into a single protein that is subsequently cleaved into smaller functional units, including RNA polymerase
- RNA polymerase replicates the positive RNA, producing a negative RNA template, which is used to synthesise more positive RNA
- the new positive RNA strands are packed with proteins to form new viral particles
10
Q
RNA viruses- negative sense ssRNA
A
- the virus has RNA polymerase needed to make positive mRNA from negative RNA
- the positive mRNA is used to produce viral proteins and replicate the genome
- the newly formed proteins and replicated RNA assemble into new viral particles
11
Q
RNA retrovirus
A
- the virus has reverse transcriptase needed to transcribe RNA into viral DNA
- the newly formed viral DNA integrates into the host cells genome with the help of integrase
- the host cells machinery transcribes and translates the integrated viral DNA into proteins
- these newly created proteins assemble with new RNA to form new viral particles
12
Q
lytic cycle
A
- the virus inserts the viral nucleic acid into the cytoplasm of the host cell
- the viral genome is replicated independently of the host cell genome
- eventually a large number of viruses are assembled
- the host cell will lyse and the virus will be released and infect more cells
13
Q
latency
A
- the virus doesn’t take over the metabolism of the infected cell but remains dormant
- the viral nucleic acid may be reactivated at any time
14
Q
episomal latency
A
- the viral nucleic acid remains inactive but free in the cytoplasm or nucleus
15
Q
proviral latency
A
- the viral nucleic acid becomes incorporated into the DNA of the host cell
- it is now termed a provirus
16
Q
why are viruses not living cells?
A
- they are much smaller than cells and have no cellular structure
- they cannot reproduce by themselves, and can only reproduce within a living host cell
- they do not perform any other life processes etc respiration, movement, excretion
- they don’t grow or develop in complexity
- they are utterly dependant on the host cell
17
Q
antivirals
A
- viral infections are difficult to treat because viruses lack any metabolism of their own
- effective antivirals inhibit viral replication by host cells
18
Q
when antivirals have not been developed
A
disease control must rely on preventing its spread. in the 2014 ebola outbreak in west africa there were no effective antiviral medications. the control of the outbreak solely relied on attempts to prevent the spread of the virus
19
Q
ethical implications of using untested drugs
A
- difficult to obtain informed consent
- unknown side effects
- may not be as effective as the current accepted treatment
20
Q
timeline for drug development
A
- phase 1: drug or vaccine tested on a small number of healthy participants to assess safety
- phase 2: over 100 participants who have the disease to study efficacy
- phase 3: over 1000 participants to study safety, efficacy and dosing
