Viruses And Other Infectious Agents Flashcards

1
Q

Describe the initial experiments used to discover the existence of viruses

A

Filtration experiments:

  1. extract and filter infectious liquid
  2. inject filtered liquid into healthy animal
  3. filter liquid cause disease
  4. infectious agent is smaller than bacteria therefore in the liquid
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2
Q

Explain why Microscope techniques available in the late 1800s where not capable of visualizing viruses and what form of microscopy was able to confirm the existence of viral particles

A

Viruses are so small they’re unable to be seen with the light microscope. In the late 1930s electron microscope’s were used to visualize the tobacco mosaic virus 160,000 times magnification

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3
Q

Define the concept of host range as it applies to viruses and based on the principle of virus structure and function explain why viruses are generally able to infect a specific type of cell

A

Host range; viruses tend to infect specific cell types

Narrow groups of cell types to infect evolutionarily types of similarities narrow key truly unique to the cell type that infects

**

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4
Q

Draw the structure of the virion and describe the major common and components found in a virion And distinguish the structure is not an animal and not animal viruses

A

Genome type and composition: DNA/our name can be single or double stranded sense or anti sense

Capsid (and capsomere) Protein coat always present surrounding nucleic acid
capsomere Visual proteins up unit that forms a protective shell known as capsid

Spikes (and composition) : Glycoprotein complexes use that to host cell that come off the capsid

Envelope: Outer lipid layer
( only an animal virus )

*draw

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5
Q

Generally describe how viral taxonomy it works and understand the general limitations of the size of viral genome

A

Based on the nature Of the viral genome smallest set of proteins that a virus needs to carry out its life cycle

DNA viruses: ds dna, ss dna,

RNA viruses: ds rna,+ss rna, -ss rna

Retro viruses: HIV 9 genomes total
Ss rna retro, ds dna retro
Any group of RNA viruses in which insert a dna copy of the genome into the host in order to replicate

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6
Q

Know the common viral morphologies

A

Helical viruses : tobacco mosaic virus, capsid with rna

Polyhedral viruses : made of adenovirus

Enveloped viruses (only animal) 
May be helical or polyhedral 

Complex viruses: (bacteriophage)
Head contains dna, collar, sheath, base plate tail fibers
Infect only bacteria, can kill bacterial cells
**know how to draw and label **

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7
Q

Describe the general function of spikes on viruses, and in particular the function of the spikes surrounding the influenza virus and how spike composition defines subtype

A

Spike composition determines the subtype

Subtype h1n1 h2n1 etc**

Hemagglutinin: Causes red blood cells to clump allows virus to enter cell

Neuraminidase: Cleaves sialic acid at cell surface, allows virus to leave cell.

Spike proteins are specifically made to attach to certain cell receptors that may only be present in specific cells

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8
Q

Explain the methods by which scientist grow viruses for research or vaccine production

A

Phage growth on a bacterial lawn and plaque formation: Used to kill the bacteria with the virus attacks bacterial infection with bacterial phage specific bacteria that formation indicates viral infection (holes in plaque)

Cell culture and that cytopathic affect on virally infected eukaryotic cells: Host cell grown in lab infected with the virus cutopathic affect disease change due to viral infection of cell

Uses of embryonated egg: Used for many viruses vaccine today flu virus

Virus production in living organisms: ?
**

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9
Q

Describe the major differences and similarities between the lytic and lysogenic cycles

A

Lytic cycle: Virus makes everything needed to assemble new virus kills infected cell upon exit. Model virus- bacteriophage T4

Lysogenic cycle : Virus integrates into host chromosome waiting for the right moment to emerge. model- bacteriophage lambda

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10
Q

For the lytic cycle Explain the steps by which a bacterial phage carries out it’s reproductive cycle and the affect on the bacterial host resulting from page infection

A

Attachment: to host cell

penetration: of host cell by viral DNA
- virus rudely injects it’s DNA into cell and destroys host cell DNA

biosynthesis: of viral components
- uses host cell’s ribosomes and resources to make phage components using information in phage

maturation: of viral components into mature virions
release: of freshly made viral particles by cell lysis (rupture)

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11
Q

For the lysogenic cycle Describe the steps by which a phage integrates it’s genetic information into the bacterial chromosome to form prophage And the effect this can have on the host bacterium

A

Attachment: to host cell

penetration: injects DNA into host cell

integration and prophase formation: viral DNA integrates into host chromosomes
Prophage viral genome integrated into host genome changes infectious properties of bacterium

reproduction of lysogenic bacterium: reproduces normal binary fission

Phage conversion: replicated during division

Prophage exit from lysogenic cycle
Escapes occasionally and renters lytic cycle

**examples: diphtheria, botulism, pathogenic E. coli , toxic shock syndrome

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12
Q

Describe the major differences between the reproductive cycle in an animal and virus phages

A

Entry of virion into cell via receptor-
mediated endocytosis: entire virion is brought intact into the cell
or
fusion: envelope fuses with plasma membrane, capsid enters

Uncoating: capsid disassembles releasing viral genetic information

Release of newly formed viruses by budding
Forming the envelope around the capsid

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13
Q

List some common DNA viruses and explain the shared reproductive characteristics

DNA viruses that infect eukaryotic cells

A

Canine parvovirus
Herpesvirus (cold sores)
Papovavirus (hpv)
Pox viruses (smallpox): bring own enzyme to make mRNA

Key features: dna is transcribed to mRNA in the nucleus
Or
DNA is transcribed to mRNA in the cytoplasm using a viral enzyme

Transcribed mRNA then used to make virions

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14
Q

List common RNA viruses and describe how viral components are produced within an infected cell

A

Key feature: virus contains its own RNA- dependent rna polymerase which make mRNA in the cytoplasm

Examples:
Poliovirus
Lyssavirus (rabies)
Filovirus (Ebola)

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15
Q

List some common retroviruses explain how retroviruses can integrate their genetic information into the host cells genome

A

Describe how integration could lead to

Latent infections
Can remain hidden in genome forever

cancer
Can cause if integrated into bad spot in host cells genome

provirus formation: viral ds dna integrates into host genome as a provirus

Contain reverse transcriptase: create ds dna from viral rna

Examples: lentiviruses (hiv)
Delta retroviruses (human t lymphotrophic virus- causes cancer )
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16
Q

Describe the sub viral infectious particle called a viroid and explain how the function of viroids may relate to the origin of life on earth

A

Subviral RNA based infectious Agent

RNA only no protein or capsid

Infect some plants

Some auto catalytic - capable of copying themselves given enough rna nucleotides

RNA world hypothesis: self replication rna molecules gave rise to life on earth

17
Q

List some notable prion diseases and explain the process by which a prion causes an infection

A

Transmissible spongiform encephalopathy:
Spongy brain and spinal tissue, progression untreatable leads to death

Preventative measures:
Destroy denature prion

Mechanism of infection and disease progression: disease transmissible by consumption of prion protein

Examples: mad cow disease (cow)
Creutzfeld-Jacob disease (human)
Scrapie (sheep)
Chronic waisting disease (deer)