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MICR 262 > (LE4) Virology > Flashcards

(LE4) Virology Flashcards

1
Q

What are general characteristics of a virus?

A
  • Acellular (can’t live alone)
  • Obligate intracellular parasites
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2
Q

What is the general structure of a virus?

A

Nucleic acid core
- single-stranded or double-stranded
- whole or segmented

Capsid
- protein coat

Some viruses have an envelope
- plasma membrane derived from host
- viral spikes

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3
Q

What are the types of capsid shapes a virus can have?

A
  1. polyhedron
  2. Helical (tube)
  3. complex
    - both
    - e.g. bacteriophage

All can have envelope

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4
Q

What is the smallest known virus? Largest?

A

Polio: 30 nm

Ebola: 1 µm

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5
Q

What are the two leading hypotheses for the origins of viruses?

A
  1. Devolved cells adapting to parasitic lifestyle while losing the ability to replicate on their own
  2. Self-replicating nucleic acids that evolved with cells
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6
Q

How is viral taxonomy determined?

A

Based on type and arrangement of nucleic acids
- can be based on capsids, morphology, envelope, and size
- family names
- hard to differentiate genera and species

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7
Q

What is a common characteristic of all Herpes viruses?

A

they all show latency

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8
Q

How do you cultivate a virus in the lab?

A

Requires cell culture
- embryonated eggs
- live animal or plant hosts
- bacteria lawn

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9
Q

What are plaques on a bacterial lawn?

A

Areas where virus has killed bacteria and spread

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10
Q

What is a primary culture?

A

tissue/cells removed from the host organism
- Cons: kills host and is temporary

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11
Q

What is an immortalized culture?

A

Derived from cancer cells -> indefinite growth
- e.g. HeLa cells

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12
Q

What is a bacteriophage? Briefly describe its morphology

A

A virus that infects bacteria

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13
Q

What type of lifecycle is performed by T-even phages? What are the steps?

A

Lytic lifecycle

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14
Q

What distinct phase in Phage lambda’s lifecycle allows it to lay “dormant”? What happens in that phase?

A

Lysogenic phase

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15
Q

What is a prophage?

A

Viral DNA incorporated into the bacterial chromosome

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16
Q

What triggers prophage to enter the lytic cycle?

A

Induction event
- starvation, chemicals, UV light, etc.

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17
Q

What is transduction?

A

horizontal gene transfer via a bacteriophage

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18
Q

What is specialized transduction?

A

Viral DNA goes into a specific part of bacterial DNA and takes specific genes with it

19
Q

What is generalized transduction?

A

Viral DNA is randomly put into the chromosome and random bacterial DNA gets taken with it
- entire chromosome is broken apart when the phage is lytic
- recombination of bacterial DNA with the new genes

20
Q

What virulence factors can generalized transduction cause?

A
  • Shiga toxin plasmid in E. coli
  • antibiotic resistance
21
Q

What is the first step of the animal virus lifecycle?

A

Adsorption (attachment)
- specific cell type (receptor specificity)
- host specificity

22
Q

What is the second step of the animal virus lifecycle?

A

Penetration

23
Q

What is the third step of the animal virus lifecycle?

A

Uncoating
- release genome into cell
- destroy capsid and vesicle

24
Q

What is the fourth step of animal virus lifecycle?

A

Biosynthesis
- Replication -> make genome (host machinery)
- protein synthesis TXN, TSN
i. capsid proteins
ii. viral spikes

25
Q

What is the fifth step of animal virus lifecycle?

A

Assembly (maturation)

26
Q

What is the sixth step of animal virus lifecycle?

A

release:

Lysis of host cell: non-enveloped viruses
Budding: enveloped viruses
- exocytosis -> taking host PM -> envelope

27
Q

What is one instance phage therapy is used for?

A

Diabetic ulcers
- antibiotic resistance

28
Q

During adsorption, how do non-enveloped viruses attach compared to enveloped viruses?

A

Non-enveloped: capsid binds receptor

Enveloped: viral spike binds receptor

29
Q

How do non-enveloped viruses penetrate compared to enveloped viruses?

A

Non-enveloped: adsorb then trigger endocytosis to enter host cell
Enveloped: fuse the envelope to cell membrane to enter host cell. Viral envelope left on plasma membrane (recognized by T-cells)

30
Q

What virus can remain latent in neurons after uncoating?

A

herpesvirus family: HSV-1, HSV-2, VZV

31
Q

How do DNA viruses replicate?

A

Uses host cell machinery

32
Q

What are the 2 types of ssRNA viruses?

A

(+) sense strand - RNA can act like mRNA and be translated directly by host ribosome
- has AUG codon 3’-AUG…..-5’

(-) sense strand - template for mRNA, cannot be translated directly
- Has UAC codon-> translated into AUG on mRNA 5’-UAC….-3’

33
Q

What enzymes are used by viruses for replication?

A

RNA-dependent RNA polymerase
- Template: RNA
- Product: RNA

Reverse Transcriptase
- Template: RNA
- Product: DNA
- Only known to be used by retroviruses e.g. HIV

34
Q

Describe viral replication for +ssRNA

A
35
Q

Describe viral replication for -ssRNA

A
36
Q

What virus causes Burkitt’s lymphoma?

A

Epstein-Barr virus (EBV)

37
Q

What virus causes cervical cancer?

A

HPV-8 and HPV-16

38
Q

What virus causes liver cancer?

A

Hep B and Hep C

39
Q

What virus causes Kaposi’s Sarcoma?

A

Human Herpes Virus (HHV-8) (with assistance from HIV)

40
Q

What virus causes T-cell leukemia/lymphoma?

A

Human T-cell Leukemia virus (HTLV-1)

41
Q

What factors allow viruses to cause cancer in the host?

A

Contains oncogenes (genes that have capacity to cause cancer) which are involved in cell growth cycle

Provirus (HIV and HPV) incorporate viral genome into host cell chromosome disrupting tumor suppressing genes. e.g. contact inhibition genes

42
Q

What are prions?

A

proteinaceous infectious particles
- misfolded proteins with ability to transmit misfolded shape onto normal variants of same protein
- usually found in brain proteins
- needs to be able to replicate itself to be infectious
- can cause same misfolding in normal proteins

43
Q

Briefly describe Pruisner’s research on Kuru

A

Filtered out all microbes and destroyed DNA/RNA viruses. Then, denatured proteins with urea and phenol and concluded it was a new protein-based pathogen

MICR 262 (30 decks)

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