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Bio 55 > Viruses, Prions, Viroids > Flashcards

Viruses, Prions, Viroids Flashcards

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1
Q

What are characteristics of viruses?

A

-minuscule, acellular infectious agents
-have either DNA or RNA
-causes many infections of humans, animals, plants and bacteria (all living organisms)
-causes most of the diseases that plague the industrialized world
-cannot carry out any metabolic pathway
-neither grow nor respond to the environment
-CANNOT reproduce independently
-recruit a cell’s metabolic pathways to increase their numbers
-no cytoplasmic membrane, cytosol, organelles (one exception)
-have extra cellular and intracellular state

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2
Q

What is the extracellular state of viruses?

A

-called virion
-protein coat (capsid) sorrounding nucleic acid
-nucleic acid and capsid also called nucleocapsid
-some have phospholipid envelope (around capsid)
-outermost layer provides protection and recognition sites for host cells

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3
Q

What is the intracellular state of a virus?

A

-capsid removed
-nucleic acid only/ all that is left
(Genome)

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4
Q

What is a capsid?

A

*PROTEIN COAT
-provide protection for viral nucleic acid
-means of attachment to host’s cells
-composed of proteinaceous subunits called “CAPSOMERES”

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5
Q

Are capsomeres made of single or multiple types of proteins?

A

Multiple types of proteins

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6
Q

What makes up capsids?

A

Capsomeres together make up capsids

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7
Q

Can viruses be DNA, RNA, or both?

A

Viruses can be either DNA or RNA but never both.

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8
Q

What types of DNA or RNA can viruses be?

A

-dsDNA (double stranded DNA)
-ssDNA (single stranded DNA)
-dsRNA (double stranded RNA)
-ssRNA (single stranded RNA)

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9
Q

Viruses can usually appear__________________ or ___________________

A

-linear and segmented
-single and circular

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10
Q

Most viruses are host ____________.

A

-specific

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11
Q

Give example of host specific viruses.

A

-virus that infects liver only affects liver cells

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12
Q

What is generalists?

A

Infect many kinds of cells in many different hosts

(Usually stick to same types of cells)

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13
Q

Can viruses mutate and infect other host?

Ex. Horse——->Human

Y/N

A

YES

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14
Q

What 3 basic shapes are viruses?

A

-Helical (Ebola)
-polyhedral (20 sides)
-complex (nucleocapsids w/ other membranes & proteins involved)

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15
Q

What type of microscope can you see viruses in?

A

Light microscope

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16
Q

Viruses are usually ___________

A

Geometric

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17
Q

What creates the virus shape?

A

Capsid

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18
Q

What is the viral envelope composed of ?

A

-phospholipid bilayer
-proteins

*some proteins virally coded glycoproteins (spikes)

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19
Q

Envelope’s proteins and glycoproteins often play role in_________________.

A

Host recognition

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20
Q

When a virus has a “corona” or “crown” what does this mean ?

A

It is covered in spikes

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21
Q

The parts of a bacteriophage virus? (Virion)

A

-base
-tail
-sheath
-DNA
-capsid
-head
-tail fibers (legs)

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22
Q

What are they 2 types of viral replication processes called? (Bacteria)

A

-Lytic replication
-lysogenic replication (lysogeny)

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23
Q

What is lytic replication ?

A

-replication cycle usually results in death and lysis of host cell.

(Related to lysis; bursts out of cell)

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24
Q

Stages of the lytic cycle?

A

-attachment
-entry
-synthesis
-assembly
-release

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25
Q

What is lysogeny (lysogenic replication)

A

-lytic cycle is delayed, virus infects bacterial dna, which then replicates on its own until some external factor activates the lytic cycle.

-modified replication cycle
-infected host cells grow and reproduce normally
-temperate phages—-prophages-inactive phages
-lysogenic conversion results when phages carry genes that alter phenotype of a bacterium (transduction)

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26
Q

Replication of animal viruses have __________ ____________ replication pathways as bacteriophages.

A

Same basic

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27
Q

Differences result from:
(ANIMAL VIRUSES replication vs. bacteria)

A

-presence of ENVELOPE around some viruses
-eukaryotic nature of animal cells
-LACK of cell wall in animal cells

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28
Q

In replication of animal viruses how does the virus find the host cell?

(Attachment of animal virus)

A

Chemical attraction

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29
Q

Do animal viruses have tails?
Do animal viruses have tail fibers?

A

-NO
-NO

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30
Q

What are viruses without envelopes called?

A

-Naked Viruses

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31
Q

What are the 3 mechanisms of viral entry for animal viruses?

A

-Direct penetration
-Membrane Fusion
-Endocytosis

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32
Q

Explain Direct penetration of a virus

A

-virus without an envelope’s (naked virus) capsid attaches to receptors on cytoplasmic membrane and viral genome leaves capsid and penetrates host cell directly (only the genome, no capsid)

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33
Q

Explain membrane fusion of a virus .

A

ENVELOPED VIRUS attaches to receptors on cytoplasmic membrane of the host and envelope fuses with cytoplasmic membrane leaving behind viral glycoproteins , both capsid and genome enter the host cell and capsid begins “uncoating” inside the cytoplasm exposing the viral genome .

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34
Q

Explain endocytosis of a virus

A

Happens when EITHER enveloped or naked virus lands on plasma/cytoplasmic membrane and the membrane of the host ENGULFS the virus, which proceeds into the cytoplasm where it breaks down to reveal viral genome.

*absorbed by phagocytosis

35
Q

In synthesis of animal viruses,
It requires various strategies depending on its?

A

Nucleic acid

36
Q

In replication of animal viruses,
Where do DNA viruses enter?

A

The nucleus

37
Q

In replication of animal viruses,
Where do RNA viruses replicate?

A

Cytoplasm

38
Q

How is mRNA synthesized?
(Animal replication)

A

RNA polymerase

39
Q

DNA-containing viruses replicate their DNA in?

(Animal replication)

A

Nucleus of host cell
(By using viral enzymes)

40
Q

Where is the capsid and other proteins synthesized for DNA-contains viruses

(Animal replication)

A

In the cytoplasm
(Using host cell enzymes)

41
Q

What serves as a template for nucleic acid replication ?

A

-Viral RNA

(Viral mRNA?)-Have to ask prof if its the same thing ?

42
Q

In a retrovirus, how is DNA transcribed from the +RNA?

A

-uses enzyme Reverse Transcriptase

43
Q

What is a common example of a retrovirus?

A

HIV

44
Q

Where do most DNA viruses assemble?

(Animal virus)

A

In the nucleus.

45
Q

Where do most RNA viruses develop?

(Animal viruses)

A

Cytoplasm

46
Q

Number of viruses produced depends on type of virus and size and _________ ___ ________ ______

A

-health of host/ cell

47
Q

Enveloped viruses cause persistent infections. Explain and give example.

A

-virus hangs around the cytoplasm

_ex. HERPES

48
Q

Naked viruses are released by ?

A

Exocytosis

49
Q

What is latency?

(Replication of animal viruses)

A

When animal viruses remain DORMANT/INACTIVE in host cells

50
Q

How long can a virus be prolonged or latent?

A

Any length of time: days, weeks, months, years

51
Q

Some latent viruses ____________ become incorporated into host chromosome

A

Do not

52
Q

Incorporation of _____________ into host DNA is __________

A

-Viral genome

-permanent

53
Q

Any DNA that inserts into animal genome is permanent.

T/F?

A

TRUE

54
Q

Can viruses cause cancer ?

A

Yes, can sometimes cause cancer.

55
Q

Cells are programmed for cell division a __________ number of times.

A

Specific

56
Q

What is neoplasia?

A

-uncontrolled cell division in multicellular animal

-on/off switches not working properly

57
Q

Mass of neoplasticism cells is called ?

A

Tumor

58
Q

What is a benign tumor?

A

Tumor that is not going to do anything

59
Q

What is a malignant tumor?

What is metastasis?

A

-Tumor that can spread by metastasis (cancerous)

-pieces of malignant tumor break away/land somewhere else in the body

60
Q

What is the oncogene?

A

It is a tumor gene

61
Q

What are some environmental factors that contribute to the activation of oncogenes?

A

-ultraviolet light
-radiation
-carcinogens
-viruses (only some, not all)

62
Q

Viruses cause what percentage of human cancers?

A

20-25%

63
Q

Some viruses carry copies of _________ as part of their genomes.

A

Oncogenes

64
Q

Some viruses _________oncogenes already present in host.

A

Promote

65
Q

Some viruses ___________ interfere with tumor repression .

A

Interfere

66
Q

Specific viruses are known to cause about ________% of human cancers

A

15

67
Q

Can viruses be seen in a light microscope?

Y/N?

A

No

68
Q

What CAN you study about viruses in a light microscope?

A

You can study host cells that have been infected using a light microscope.

69
Q

What are the 2 types of cell cultures?

(Culturing viruses in cell (tissue) culture)

A

-Diploid cell cultures
-continuous cell cultures

70
Q

Explain culturing viruses in cell (tissue) culture

A

Consists of cells isolated from an organism and grown on a medium or in a broth

71
Q

Are viruses alive?

A

(Not by definition)

-some consider them complex pathogenic chemical

-others consider them the least complex living entities

72
Q

Why do some believe that viruses are least complex living entities ?

A

-use sophisticated methods to invade cells
-have the ability to take control of their host cell
-are able to replicate themselves

73
Q

Define coronaviruses

A

-large family of viruses causing upper respiratory infections

74
Q

Explain the following :

SARS-CoV
MERS-CoV
SARS-CoV-2

A

-Severe Acute Respiratory Syndrome (NOV 2002)
-Middle East Respiratory Syndrome (2012)
-Severe Acute Respiratory Syndrome causing Corona virus [COVID-19] (2019)

75
Q

Characteristics of Viroids

A

-Extremely small, circular pieces of RNA
-Similar to RNA viruses, but LACK CAPSID
-may appear linear due to H bonding

76
Q

Explain the structure of a viroid

A

-circular single-stranded RNA with some pairing between complementary bases and loops where no such pairing occurs.

77
Q

What are other parasitic particles ?

A

-viroids
-prions

78
Q

Characteristics of prions?

A

-proteinaceous infectious agents
-Cellular PrP protein
-Prion PrP
-Normally, nearby proteins and polysaccharides for PrP into cellular shape
-PrP mutations result in formation of prion PrP

79
Q

Explain cellular PrP protein

A

-in glial cell membranes of the brain
-made by all mammals
-normal structure with a-helices called cellular PrP

80
Q

Explain Prion PrPed

A

Disease-causing form with B-pleated sheets called prion PrP

81
Q

Explain prion diseases

A

-fatal neurological degeneration, fibril deposits in brain, and loss of brain matter.
-large vacuoles from in brain
-spongiform encephalopathies (looks like sponge, encephalo=in brain, Pathies=disease

82
Q

How are prions destroyed ?

A

Only destroyed by incineration or autoclaving in 1N NaOH

-under pressure

83
Q

Vacuoles form from prions make it look ?

A

Makes tissue look spongy

Bio 55 (19 decks)

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