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Microbiology > Lesson 3.3 - Viruses > Flashcards

Lesson 3.3 - Viruses Flashcards

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Biology 101 flashcards
1
Q

Characteristics of Viruses

A
  • nm (10-9) to um (10-6)
  • obligate intracellular molecular parasites
  • acellular, infectious, diverse
  • DNA or RNA
  • lacks ribosomes & metabolic pathways
  • mutations; responds to natural selection
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2
Q

Viral sizes

A

idkkkk

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3
Q

Viral genomes

A
  • Most are small (5-500 kb)
    • May consist 1+ chromosomes
    • Circular or linear
    • DNA or RNA (some have tRNA)
    • ss or ds
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4
Q

Viral Mutation Rate

A
  • abt. 1 in 10k nts
    • Humans are abt 1 in 1 billion
  • No repair system
  • Frequent reassortment
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5
Q

Viruses in Nature

A
  • Earth’s most abundant biological particles
  • Found in concentrations 10X higher than prokaryotes
  • Don’t always harm host
    • i.e. anelloviruses in blood
    • Nasal secretions, saliva, bile, feces, tears, semen, breastmilk, urine
  • Some benefit host
    • Transduction (bacteriophage)
    • Human genome full of dysfunctional retroviruses
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6
Q

Dimitri Ivanowsky (1892)

A
  • Botanist
  • Causal agent could pass through ceramic filter
  • Flitrate contained poison venom
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7
Q

Martinus Beijerinck (1898)

A
  • Microbiologist; repeated Ivanowsky experiments
  • Virus inactivated by boiling contagious living fluid
    • Tobacco mosaic virus (TMV)
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8
Q
  • Yellow Fever (1902)
  • Rous Sarcoma Virus (1911)
  • Bacteriophages (1915)
  • Fertilized chicken eggs (1931)
A
  • Mosquito vector
  • Oncogenesis
  • -
  • Animal virus cultivation
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9
Q

Crystallization of TMV discovered by [who]

A
  • Stanley (1935)
    • Nobel Prize in Chemistry (1946)
  • Proof that viruses were not cells; made of protein & nucelic acid (DNA or RNA); require a host cell for replication
  • Electron microscope images n/a until 1947
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10
Q

Virus Methods of Infection

A
  • Mucous membranes
    • Rub eyes, inhale droplets
  • GI tract
    • Contaminated food/water, fingers in mouth (ooo)
  • Trauma
    • Animal bite, contaminated needles, mech. injury
  • Genitourinary tract
    • Sexual transmission
  • Plant viruses/seed borne, arthropod vector
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11
Q

How do viruses make us sick?

A
  • Homeostasis disrupted; host cells manipulated to produce viruses
    • Cell lysis, changes in size/shape, nuclear inclusion bodies, cytoplasmic inclusion bodies, mutations, transform to cancer cells, multinucleated cells
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12
Q

Zoonosis

A
  • Animal origin / host / reservoir
  • Naturally transmissible (vertebrae animals to humans)
    • Some b humanized & unaffect animals
      • measles, HIV, Sars-CoV-2
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13
Q

Ebola by [what animals]

A

bats

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14
Q

Rabies by [what animals]

A

mammals

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15
Q

Influenza by [what animals]

A

birds and pigs

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16
Q

SARS by [what animals]

A

civets

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17
Q

Middle East Respiratory Syndrome (MERS) by [what animals]

A

dromedary camels

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18
Q

Sars-CoV-2 by [what animals]

A

bats; suspected pangolins

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19
Q

What does it mean when viruses are polythetic?

A

In a group that cannot be defined on basis of any single shared character, but on overlapping combinations of characters

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20
Q

Type of nucleic acids [Viruses]

A
  • DNA, RNA (some have tRNA), ss, ds
  • Linear, circular
  • (+) strand vs. (-) strand
  • no universal gene
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21
Q

Shape [Viruses]

A
  • Capsid structure; presence/absence
  • Presnce of additional structures
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22
Q

What are some organisms that viruses parasitize?

A

Bacteria (bacteriophages), Archaea (archaeaphages), insects, mammals, birds, fish, amphibians, plants, amoeba, fungi (mycoviruses), crustaceans

23
Q

Viruses can be classified by taxonomic terms, especially families such as the ____________ suffix

A
  • viridae
  • Governed by International Committee on Taxonomy of Viruses (ICTV)
24
Q

What is the host for Mimivirus?

A

Acanthamoeba polyphaga

Originally thought to be Gram (+)

25
Q

Where do virsues fit in the tree origin of life?

A

No single evolutionary origin; instead are vehicles of transfer

26
Q

Plus (+) strand RNA viruses

A

Consists mRNA directly translated into proteins

27
Q

Minus (-) strand RNA viruses

A

Contains viral RNA complementary to viral mRNA

28
Q

Retroviruses

A

makes a DNA copy of its RNA genome that is inserted into the DNA of the host cell

29
Q

Viron [and terms used to describe it]

A
  • Individual complete virus particle
    • Helical
    • Polyhedral (many sided)
      • Icosahedral (20)
    • Binal
      • Pleomorphic (irregular)
30
Q

Define capsid.

A
  • Protein shell enclosing nucleic acid
  • Built of capsomeres
    • Can be 100s of same or different
  • ​​​Nucleocapsid: nucleic acid + capsid
31
Q

Define envelopes.

A
  • Lipid bilayer derived from host cell
  • Contain viral glycoproteins for infecting cells
    • i.e. Sars-CoV-2
      • [S]pike, [E]nvelope, [M]embrane. [N]ucleocapsid
  • Without envelope: naked
32
Q

Viral Host Specificity

A
  • Virion binds to host cell membrane receptor
    • Lock and Key​
  • noneveloped virus attach via arrangement/ shape of capsids
33
Q

Stages of Virus Replication

A
  • Attachment
  • Eclipse phase
    • Penetration and uncoating
    • Synthesis
    • Assembly
  • Release
34
Q

Penetration stage 😏

A
  • Nonenveloped enter by endocytosis
  • Enveloped enter by endocytosis or fusion
  • Bacteriophages puncture cell envelope & inject their DNA
35
Q

Uncoating phase

A
  • Host cell removes capsid
  • Endocytic vesicles low pH
  • Host cell proteases
36
Q

Eclipse phase

A

Interval b/t penetration and production of virions

37
Q

Synthesis phase

A
  • Viral DNA escorted to nucleus; replicated
  • Viral enzymes may be involved
  • Transcription by host
38
Q

Assembly phase

A
  • Some at plasma membrane
  • Organelles
    • RER, Golgi, mitochondria, chloroplasts
39
Q

Release phase

A

Lysis and budding are most common

40
Q

Cellular Flow of Information [in terms of Viruses]

A
  • Some follow dis, but others bend the rules to their advantage
  • (+) = sense; message
  • (-) = antisense; template
41
Q

Baltimore Classification

A
  • Classifies viruses based on genome type
    • Understand how virus replicated its nucleic acid
    • Understand how viral mRNA is synthesized
42
Q

DNA Dependent DNA polymerase

A

Enzyme that catalyzes DNA synthesis from DNA template

43
Q

RNA Dependent DNA polymerase

A

Enzyme that catalyzes DNA synthesis from RNA template

44
Q

DNA Dependent RNA polymerase

A

Enzyme that catalyzes RNA synthesis from DNA template

45
Q

RNA Dependent RNA polymerase

A

Enzyme that catalyzes RNA synthesis from RNA template

46
Q

Class I: dsDNA

A
  • dsDNA -> mRNA -> protein
    • Host DNA-dependent RNA-polymerase
  • Genome replication: dsDNA -> dsDNA
    • Host DNA-dependent DNA-polymerase

i.e. Herpes, Smallpox, HPV

47
Q

Class II: ssDNA

A
  • (+) ssDNA -> dsDNA -> mRNA -> protein
    • Host DNA-dependent DNA polymerase
    • Host DNA-dependent RNA polymerase
  • (-) ssDNA -> dsDNA -> mRNA -> protein
    • Host DNA-dependent DNA polymerase
    • Host DNA-dependent RNA polymerase

i.e. Erythroparvovirus, fifth disease, skin lesions

48
Q

Class III: dsRNA

A
  • (-) RNA -> mRNA -> protein
    • Viral RNA-dependent RNA polymerase (packaged in virion)
      • makes (+) and (-) strand copies

i.e. Rotavirus (diarrhea & vomiting)

49
Q

Class IV: (+) ssRNA

A
  • (+) RNA -> protein
    • Codes for RNA-dependent RNA polymerase
      • synthesize (-) RNA from (+) strand

i.e. Norovirus (vomiting & diarrhea), Sars-CoV-2, HepA, HepC

50
Q

Class V: (-) ssRNA

A
  • (-) ssRNA -> (+) RNA -> protein
    • Viral RNA-dependent RNA polymerase (packaged in virion)

i.e. Ebola, Measles, Influenza

51
Q

Class VI: (+) ssRNA w/ DNA intermediate

A
  • (+) RNA -> (+/-) dsDNA -> mRNA -> protein
    • Viral RNA-dependent DNA polymerase; reverse transcriptase
    • Host DNA-dependent RNA polymerase
  • Retroviruses

i.e. Lentiviruses, HIV

52
Q

Class VII: (+/-) dsDNA w/ RNA intermediate

A
  • Uses reverse transcriptase (P)
  • Incomplete dsDNA “gapped genome”
  • Last step: reverse transcriptase activity occurs inside virion
  • RNA -> DNA: not shown in image

i.e. HepB

53
Q

Baltimore Classification Group I-VII Overview

A
  • I: ds (+/-) DNA viruses
  • II: ssDNA viruses (majority (+))
  • III: ds (+/-) RNA viruses
  • IV: (+) sense ss (+) RNA viruses
  • V: (-) sense ss (-) RNA viruses
  • VI: ss (+) RNA viruses w/ DNA intermediate
  • VII: ds (+/-) DNA viruses w/ RNA intermediate

Microbiology (17 decks)

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