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DDT > DTT 17 - Viruses, Viroids, Prions and Diseases > Flashcards

DTT 17 - Viruses, Viroids, Prions and Diseases Flashcards

1
Q

virus definition

A

‘A tiny, infectious particle, consisting of a nucleic acid core surrounded by a protein coat called a capsid’.

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2
Q

smallest and largest virus and size

A

250Å (yellow fever)
2,500Å = 0.25µm (Vaccinia, Smallpox);
Å = angstrom = 0.1 nanometre

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3
Q

who discovered first virus and what virus did they discover

A

1892 by the Russian botanist Dmitri Iwanowski who was looking at ‘Tobacco Mozaic Virus’

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4
Q

properties of a virus

A 
not cellular
don't respire
have no metabolism
don't break down carbon compounds
don't die
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5
Q

3 morphological classification

A

helical
icosahedral
combined or complex

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6
Q

how else can they be classified

A

based on nucleic acid

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7
Q

what additional property do some viruses have

A

Some viruses have a lipoprotein envelope in addition, which is derived from the membrane of the host cell.

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8
Q

how does virus propagate

A

The virus enters via sent into cytoplasm in a vacuole via the cell membrane
protein capsule left on cell’s surface
Viral nucleic acid is then released to take over the genetic machinery of the host cell
Viral DNA becomes incorporated into the DNA of the host, assuming command of genetic control.
The host synthesises viral proteins rather than its own so that new virus particles
are generated and eventually released, completing the life cycle.

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9
Q

examples of viral infection in human body other than COVID

A

meningitis
pharyngitis
Hepatitis
Smallpox

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10
Q

6 stages of viral propagation

A
  1. attachment - interaction of virion w/ specific receptor site on host cell’s surface
  2. penetration - viral particle enters cell via endocytosis look like endosomes
  3. uncoating - viral nucleic acid is removed from capsid
  4. eclipse/replication - viral particles are now small non-infective subunits in host cell
  5. assembly - new viral genomes is formed
  6. release - non enveloped viruses cause cell of host to burst and leave the host cell
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11
Q

describe process of endocytosis when host cell uptakes virus

A

virus meets plasma membrane of host cell
binds to receptors and plasma membrane surrounds virus
endosomal vesicle surrounds virus as it moves in to cytoplasm
vesicle is released from vesicle but virus leaves behind capsid

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12
Q

DNA viruses

A

DNA viruses - enter host cell’s nucleus and are replicated and transcribed in nucleus except retroviruses

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13
Q

RNA viruses

A

replicated and transcribed in cytoplasm except retroviruses

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14
Q

RNA Virus replication

A

viral nucleic acid alters genetic expression of host and instructs it to synthesize the building blocks for new viruses

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15
Q

RNA virus protein synthesis

A

RNA virus used for synthesis of viral proteins (translation0

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16
Q

polarity of RNA virus

A

whether or not it can be used directly by ribosomes to make proteins

17
Q

what does polarity of RNA virus determine

A

determines the

replicative mechanism;

18
Q

what other factor determines polarity of RNA virus

A

the other major criterion is whether the genetic material is single-stranded or double-stranded.

19
Q

what enzymes do RNA viruses use to create copies of their genomes

A

their own RNA replicase

20
Q

How does rubella virus propagate into host cell

A

virus binds to specific receptors of host cells plasma membrane
membrane surrounds virus
virus enters cytoplasm of host cell
viral nucleic acid is released from capsid and enters nucleus of host cell and replicates
it is then transcribed into mRNA
Viral mRNA directs ribosomes to synthesise viral proteins
vesicles transport glycoproteins to host cell membrane
virus is fully assembled and released

21
Q

describe shape of rubella virus

A

icosahedral shaped vorus

22
Q

symptoms of rubella measles

A

red rash and fever and cause heart failure

23
Q

effects of viral propagation on their host

A

benign or malignant growths

asymptomatic

24
Q

lytic infection

A

enzymes produced which erode the cell wall
(bacteria)/ cell membrane and cause the cell to
rupture;

25
Q

lysogenic infection

A

here viral DNA/RNA becomes incorporated into the genome of the cell and coexists with the cell;

26
Q

treatment of virus infection

A

viral chemotherapy
acyclovir - cold sore creams on Herpes virus
Interferon - used to treat AIDS

27
Q

what viruses can cause human cancers

A

Papilloma wart virus and cervical cancer (Barton, 1994)

Epstein-Barr virus - Burkitt’s lymphoma

28
Q

human papillomavirus

A

DNA virus

causes warts and non-malignant tumours

29
Q

examples of subviral particles

A

viroids

prions

30
Q

definition of subviral particles

A

Infectious agents smaller by an order of magnitude than viruses have been identified in recent years

31
Q

describe viroids

A 
Short single strands of RNA;
• Circular structures of 250-400 nucleotides
• Don’t code for any proteins;
• No protective coat (unlike viruses)
• Copied by the host RNA polymerase;
• Infect plant cells.
32
Q

what are prions short for

A

‘Proteinaceous infectious particle’

33
Q

what year were prions discovered

A

1982

34
Q

describe prions

A

Even smaller than a viroid and consisting of just a protein of 208 Amino Acids;
• Only infectious agent without nucleic acid;
• Induces normal PrP proteins to misfold thus forming
another prion

35
Q

what disease are prions involved in humans

A

spongioform encephalopathies
long incubation periods
usually fatal outcomes

36
Q

another example of prions in humans

A

kuru - transmitted by eating corpses

consumption of infected human brain tissue

37
Q

where is kuru found

A

new guinea

38
Q

what organs does kuru affect

A

nerves and brain

DDT (21 decks)

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