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46 Cards in this Set
- Front
- Back
Definition of virus
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Obligate intracellular parasite - depends on host's cell machinery to reproduce
- can be DNA or RNA |
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Viral lysogeny
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Integration of viral DNA or RNA into host cell genome
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Non permissive cell
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Cell that will not allow replication of particular type of strain of virus
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Permissive cell
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Cell providing machinery for virus machinery
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Latent infection
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Infection that is restricted or lacks machinery for transcription of viral genes
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Viral capsid
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Protein structure enclosing nuclear genome of virus - very solid
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Viral envelope
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Layer surrounding and forming surface of virus - comes from host's phospholipid
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Nucleocapsid
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Nucleic acid (DNA or RNA) + capsid (protein)
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Viral spikes
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Protein or glycoprotein structures on the surface of the virus (receptors)
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What can bacteriophage do when it infects bacteria
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- Antibiotic resistance
- Can kill bacteria helping in digestion - can get malabsorption |
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2 types of yellow fever
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Yellow fever is a viral disease - presents with jaundice
2 types - jungular + urban Jungular - from monkeys through mosquitos Urban - from humans through mosquitos |
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Compare viruses and eukaryotic cells in terms of :
- Nucleic acid -Proteins - Lipoprotein membrane - Ribosome - Mitochondria - Enzymes |
Nucleic acid: viruses - DNA or RNA, cells - DNA and RNA
Proteins: viruses - few, cells- many Lipoprotein membrane: viruses - envelope present in some, cells - cell membrane present in all Ribosome: viruses - absent, cells - present Mitochondria: viruses - absent, cells - present Enzymes: viruses - none or few, cells - many |
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Example of small cell
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Picornavirus
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Example of large cell
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Poxvirus
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With exception of _ all DNA viruses replicate in _
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Poxvirus
Nucleus |
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99% of DNA viruses are _
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Double stranded
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2 types of RNA viruses have segmented RNA - name them
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- Influenza - 8 segments
- Rotavirus - 11 segments |
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What kind of genome does DNA virus have
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Circular
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Morphology of viruses studies what?
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- Size
- Shape - Symmetry - Presence or absence of peplomers (virus coded glycorpoteins on the surface of virus envelope) - Presence or absence of membranes |
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Physicochemical properties of viruses
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- Molecular mass
- Buoyancy (if envelope - more buoyant) - pH stability - thermal stability - Susceptbility to detergents |
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Genome properties of viruses
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- Genome - DNA or RNA
- Size of genome - Type of strand - circular or linear - Sense - positive or negative - Segments (influenza) |
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What is responsible for cell attachment in influenza
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- Neuraminidase
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Name 3 types of viral architecture
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- Cubic (icosahedral) - adenoviruses
- Helical - orthomyxoviruses - Complex - poxvirus |
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What do peplomeres do
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Play key role in viral attachment and induction of netralizing antibodies
- Also called glycoproteins or spikes |
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Describe cubic (icosahedral) architecture
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Example - papilloma virus
2 components - capsid + genome Capsid - aggregation of capsomeres Core+ capsid - nucleocapsid |
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Describe icosahedral (cubic) + envelope architecture - give example
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- Rubella virus
- Nucleocapsid is wrapped in outer envelope - Between nuclecapsid and envelope is matrix protein |
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Describe helical architecture
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-Flexible hollow tube - capsid proteins are aggregated around it
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Name host responses to viruses
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- Asymptomatic - HIV, herpes
- Induction of cancers - HPV - Chronic progressive neurological disorder - Possible endocrine disease - diabetes |
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Cells can respond to viruses in 3 ways
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- No apparent change
- CPE and death of cell - Loss of growth control (transformation) - interfere with cell cycle (no check points) |
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3 basic patterns of infection in viral disease
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- Localized
- Disseminated - Inapparent |
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2 types of viremia
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Primary viremia - spread to other susceptible organs such as liver and spleen
Secondary viremia - dissemination to other organs such as skin |
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Difference between primary and secondary viremia
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High number of viruses - secondary viremia
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Describe entry into the host
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- Skin - most viruses enter through breach of physical integrity of skin, many viruses employ vectors
- GI tract - enveloped viruses cannot survive highly acidic environment - Respiratory - influenza - Genitourinary - HPV, herpes - Conjunctiva - adenovirus |
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Give examples of localized infections
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- Respiratory - rhinoviruses - cause common cold
- Rotaviruses - GI - cause infantile diarrhea - Papilloma virus - genital and skin epidermis - HPV |
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Give examples of systemic infection
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- Enteroviruses - primary replication in GI, secondary - lymph and CNS
- Herpes virus - primary replication in oropharynx or genitourinary tract, secondary - lymph or CNS |
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Which virus likes to hide in nervous system and where
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Herpes virus likes to hide in nervous system - in DRG
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2 main mechanisms of viral spread through host
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- Blood
- Nervous tissue |
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`How do viruses spread in nervous system
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- By direct contact with neurons at the primary site of infection or through blood
- They spread from peripheral nerves through AXONAL TRANSPORT Viruses cross SYNAPTIC JUNCTIONS |
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What is a secondary replication
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- Poliovirus- gut (primary) neurons and spinal cord (secondary)
- HIV - macrophages and CNS - Occurs |
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Antigenic shift and drift are common in what virus
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Influenza
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Antigenic drift
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Gradual accumulation of minor mutations
Net result - altered antigenicity Eventually immune system recognizes virus and clears it |
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Antigenic shift
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Sudden and major change in antigenicity
Due to RECOMBINATION of virus genome with genome of another antigenicity Immune system cannot recognize this change and virus becomes very severe CAN CAUSE PANDEMICS - avian flu |
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What allows influenza to undergo shift and drift
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NA - neuroaminidase
HA - hemoagglutinin |
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Name slow viral infections
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Measles- subacute sclerosing panencephalitis
Prions Papoviruses |
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Describe subacute sclerosing panencephalitis
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- Profound atrophy of cortex
- Loss of white matter - Ventricular enlargement |
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Describe progressive multifocal leukoencephalopathy (PML)
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- Giant astrocytes
- Oligodendrocyte inclusions |