Virology Flashcards
(16 cards)
What Are Viruses?
Sub-microscopic, Acellular, Obligate Intracellular Parasites
Describe Virus Behavior.
They Assemble, Not Grow
Dependent on host Cell function
Lack apparatus to generate ATP, carry out Protein Synthesis
What Is Known About The Origins of Viruses?
Origins Difficult To Determine:
- Viruses Don’t form Fossils
- Viruses Integrate Into Host Genomes
- Viruses Can Almost Infect Any Organism
Possible Theories
Viruses started as big bits of Cellular DNA, but became Independent Over Time
Retrograde Evolution: Evolution into a simpler form/ancestral form
Describe the Ivanovsky Experiment.
- Sap extracted from plant with TMV
- Sap passed through Porcelain Filter that Traps
Bacteria - Filtered Sap rubbed on Healthy Plant
Result:
Healthy plant became infected
Indicates Viruses are smaller than Bacteria
What Is a Typical Virion Structure?
Icosahedral, Helical or Complex
Highly Symmetric
What is The Viral Genome Composed of?
DNA or RNA but not both
DNA Types:
ds (Double Stranded)
ss (Single Stranded)
linear
circular
RNA
dsRNA
ssRNA
What Does the Baltimore Classification Categorize Viruses Based On?
- Type of Nucleic Acid (DNA/RNA)
- Strand type (Single/Double)
- Replication Strategy (How mRNA is produced)
What Are The Baltimore Classification Categories?
- dsDNA
- ssDNA
- dsRNA
- (+) ssRNA
- (-) ssRNA
- ssRNA-RT
- dsDNA-RT
Name The Stages of Bacteria life Cycle:
Attachment (Adsorption)
Penetration (Entry/Uncoating)
Synthesis
Assembly (maturation, packaging)
Release
What happens in the Adsorption Stage?
Receptors on Host Cytoplasmic Membrane bind to Virus Binding Sites
What Happens in the Penetration and Uncoating Stage (Naked Viruses)?
- Capsid and Host Cell Membrane Interact
- Interaction causes re-arrangement of Capsid proteins
- This allows Nucleic Acid Entry
What happens In The Penetration and Uncoating Stage (Enveloped Viruses)?
- Virus enters Host Cell
- Viral Envelope Removed
- Capsid Removed Enzymatically
What Happens In the Synthesis & Assembly Stage?
Viral Genome Directs Host Cell Replication + Translation machinery to Synthesize Viral Components
RNA Viruses → Encode RNA-Dependent RNA/DNA Polymerases
What Happens In The Release Stage (Naked Viruses)?
- Host Cell deteriorates
- Virus is Released
What happens In The Release Stage (Enveloped Viruses)?
Envelope obtained from host cell membrane upon budding
Envelope obtained from internal membranes
What Are the Virus Transmission Routes?
- Air-Droplets (Influenza, Measles)
- Faecal-Oral (Hepatitis A, Polio)
- Sexual (HIV, Hepatitis B)
- Vector-Borne
- Blood (HIV, Hepatitis B/C)
