Transcript 29th 30th March

VIRUSES
What is a virus?
• “Virus” from the Latin “simply liquid, poison”
• Non-living organism
• Very very very small
• Most abundant
• Dependent on other living organisms to survive
• Can infect plants, animals, bacteria,
archaebacteria, protists and fungi
Identification of a virus
Genetic material
2. Protective protein coat
1.
1. Genetic Material
• Core of virus
• Can be either DNA or RNA
• Single-stranded or double stranded
• (ssDNA, ssRNA, dsDNA, dsRNA)
• Linear, circular or segmented
2. Protective protein coat
• A.k.a. “Capsid”
• One of the following shapes:
• Helical
• Icosahedral (from “Icosahedron:” polyhedron with 20
faces) / Circular
• Complex (A combination of the two)
Some have “membranous envelopes”
• Some especially dangerous
viruses can even steal some
of the host cell membrane
• This allows them to make an
envelope, which they use to
trick the host cell into
thinking it is part of the body
Research the following
• Influenza
• Tobacco Mosaic Virus
• Human Immunodeficiency
Virus
• T4 bacteriophage
• Zika virus
• Ebola
• Herpes
• Measles
• Hepatitis C virus
• MERS
1.
ssDNA, dsDNA,
ssRNA or dsRNA?
2.
Helical? Icosahedral?
Complex?
3.
Membranous
envelope?
Structure of viruses
1.
•
Genetic material
ssDNA, dsDNA, ssRNA or
dsRNA
2. Protective protein coat
• Helical, Icosahedral,
Complex?
Antigens
• “Anti-” = Antibody
• “-gen” = producing
• Protein or sometimes long carbohydrate chain
• On the surface of viruses
Build a virus!
•
•
Choose either the virus you researched yesterday or out of the following:
•
Influenza
• SARS
•
Tobacco Mosaic Virus
• Chickenpox
•
Human Immunodeficiency Virus
•
T4 bacteriophage
• HIV
•
Zika virus
• Shingles
•
Ebola
Include the following structures:
•
•
•
•
1.
Genetic core
2.
Protective protein coat / membranous envelope
• Must be 3D
Herpes
Measles
Hepatitis C virus
MERS
Methods of infection
1.
Injection  Virus has some way of forcing its genetic material
into the host cell
2.
Fusion  If it has an envelope, the virus can simply fuse with
the host cell, and be taken in
3.
Endocytosis  The virus somehow tricks the host cell to take it
in voluntarily
Host cell
• Plants, animals, bacteria, archaebacteria, protists or
fungi
• Provides an environment where the virus can reproduce
Viral Specificity
• Viruses specific to a particular host
• Hand & glove model
Examples:
• Tobacco mosaic virus attack only tobacco plants
• Rabies: only mammals
• Swine flu: Pigs & humans
• Bacteriophage: only bacteria
If you were a virus, which cycle would you
choose?
Let’s build Lytic & Lysogenic Cycles!