Week 6, VIRUS Flashcards
Viral characteristics
Acellular, DNA or RNA only, need host cell to reproduce, infection every type of organism
General viral structure
Non-enveloped (naked) or Enveloped
Common viral shapes
Helical, Icosahedral, Complex
Bacteriophage
A type of virus that specifically infects bacteria, replicate in cytoplasm of prokaryotic cells (no nucleus)
Types of bacteriophages
Lytic phage, Lysogenic phage
Life cycle of Lysics phage infection
- Attachment
- Penetration : injection to host
- Biosynthesis : making more phage DNA or RNA
- Maturation : new phage particles are assembled
- Lysis : cell lysis and release new phages
Life cycle of Lysogenic phage infection
- Phage infects a cell
- Phage DNA integrated into host chromosome
- Prophage DNA is passed onto daughter cells
- Under stressful conditions (starvation, exposure to toxin) the prophase DNA enters lytic cycle
- Phage DNA replicate
- New phage particles are assembled
- Cell lyses, and newly made phages releases
Life cycle of viruses with Eukaryotic host
- Penetration : By endocytosis (virus being engulfed by host) or fusion ( viral envelope fuses with host membrane)
- Nucleic acid biosynthesis (DNA)
- Release
Persistent infections
- Latent infection : may stay inactive for years after initial acute infection
(Varicella -zoaster, chicken pox -shingles;Herpes simplex; Epstein-Barr, mono, MS) - Chronic infection : long-term persistence with recurring /ongoing symptoms (HIV, HPV, Hep C)
Cultivation of virus
- Vivo : within living organism (animal, plant)
- Vito : within artificial environments (agar)
Cytopathic effect
Visible cell abnormalities
Hemagglutination Assay
Blood test to detect certain virus by observing the agglutination of RBC, caused by hemagglutinins
Nucleic Acid amplification test
- PCR: To detect viral DNA in the sample
- RT -PCR : Riverse transcripts PCR , good for detecting viral RNA
Enzyme immunoassays (EIAs)
Uses antibodies to detect specific antigens with high specificity
Viroid
- Smallest infectious agent
- Circular RNA molecule that lacks protein coat
- Replicate within plant cells
Virusoids
- Survival particles, infecting plants
- Unable to replicate on their own
Prions
- Made of only protein, no RNA or DNA
- Caused by misfiring of prion protein
- Can interact with other proteins, causing them to misfold
- Accumulation of defective proteins »_space;> plaques in brain, neurodegenerative diseases
