Viruses_Bacteria_Achaea_A Flashcards
what type of parasites are viruses
obligate intracellular parasites
where does virus replicate
inside other organism’s cells
T/F every living studied organism has an associated virus
T
do viruses outnumber all other life forms
yes, by at least 10X
virology
study of viruses
living characteristics of a virus
DNA/RNA
non-living characteristics of a virus
need host cell to reproduce
no metabolism
un-responsive to stimuli
Louis Pasteur
1884
looking for rabies cause
Found nothing under microscope
speculated infectious agent was too small for microscope
Dimitri Ivanowsky
1892
passed crushed leaf extracts from tomato-mosaic virus infected plants through filter fine enough to filter bacteria. Filtered solution remained infectious
Martinus Beijerinck
1898
repeated experiment of Ivanowsky. Suggested filtered solution contained new form of agent
When did first images of viruses become visible
1937, electron microscope
most important viral taxonomic criteria
Host organisms
Particle morphology: filamentous/isometric, enveloped/naked
genome type: RNA/DNA, circular/linear, ss/ds
virus structure
nucleic acid core - made of RNA or DNA
protein capsid - consists of capsomeres
shape can be helical or icosahedral
envelope has tissue specific “spikes”
viral genome, number of genes
3 - 100
naked virus
virus without outer envelope
how does a virus bind to host cell
capsid or envelope spikes bind to receptors on the host cell’s surface
Lytic Cycle Steps
1) Bind: Virus capsid binds to cell receptors
2) Penetration: DNA/RNA penetrates cell
3) Biosynthesis: viral DNA/RNA cause viral components to be synthesized
4) Maturation: viruses assembled inside host cell
5) Release: cell bursts. Resultant viruses attack other host cells
Prophage
Viral genetic code inside Bacteria DNA
Lysogenic Steps
1) Attachment/Bind
2) Penetration
3) Integration: Viral DNA integrated into host cell’s chromosome (called a prophage)
4) Biosynthesis: Viral DNA leaves chromosome. (returns to Lytic)
5) Maturation
6) Release
Virus Types in this class
Bacteriophage
DNA Viruses
RNA Viruses
Retroviruses
Bacteriophage
viruses that attack bacteria
used in gene transfers
Hersey-Chase 1952 experiment
used T4 bacteriophage to prove DNA, and not protein, is the genetic material.
Radioactively labeled Phosphorous (DNA) and Sulfur (protein). Phosphorous entered cell, Sulfur did not
DNA Animal Viruses types
Herpesviruses Oral & Genital Chickenpox & Shingles Mononucleosis Papillomaviruses Warts Associated with cervical cancers 95%
RNA Animal Viruses
Picornavirus - small RNA virus - Polio: neuromuscular disease - Viral Hepatitis: liver infection Rhinovirus - common cold - mutates rapidly Orthomyxoviruses - flu Rhabdoviruses - rabies Hantavirus - deadly pneumonia Ebola virus - hemorrhagic fever Swine flu virus - contaminated meat
RNA Animal Retroviruses
Retrovirus: RNA Virus -> lysogenic DNA -> inserted into host genome uses reverse transcriptase enzyme HTLV - Human T-lymphotropic virus Cancer causing Virus HIV - Human Immunodeficiency virus AIDS
How does HIV enter body
through blood or body fluid contact
HIV Infection
- enters body through blood or body fluid contact
- attaches to/penatrates Helper T-Lymphocytes
- Reverse Transcriptase enzymes convert RNA viral code into DNA
- DNA prophage spliced into host cell DNA
- prophage may lie dormant or begin producing new viruses
Viroids
naked strands of RNA (no capsid)
cause plant diseases
Prions
proteinaceous infectious particles
proteins that are folded abnormally
cause enzyme changes in the brain
agents of Mad Cow Disease and Scrapies
other viral taxonomic criteria
disease symptoms
antigenicity
protein profile
host range
viral classification hierarchy
Order Family Subfamily Genus Species
Baltimore virus classification
seven groups Nucleic Acid: DNA/RNA Strandedness: ss/ds Sense: sense(+)/antisense(-) replication method
virus host range
range of cellular organisms a virus is capable of infecting
HIV Viral Tissue Tropism
T cells
Polio Viral Tissue Tropism
spinal nerve cells
Hepatitis Tissue Tropism
liver cells
