V: Introduction to Viruses
What is a “Pathogen”?
Definition: a disease causing agent.
What is a “Virus”?
Definition: a pathogen, or disease
causing agent, not considered living
because it cannot reproduce on its own.
Virus Reproduction
A virus must have a HOST CELL to
reproduce.
Structure of a “Virus”
Capsid: outer protein coat.
Genetic Material: DNA or RNA.
V: Invasion of the Virus
“Lytic Cycle”
Definition: process in which a virus
enters a cell, makes a copy of itself, and
causes the cell to burst.
“Lytic Cycle”
(Viral Reproduction)
“Stage A (1)”
The virus lands on the host cell and then
injects its genetic material into the host
cell.
“Stage B (2)”
The virus using the host cell to synthesize,
or make, viral proteins (capsids) and
nucleic acids (genetic material-DNA or
RNA).
“Stage C (3)”
The virus assembles (puts together)
capsids and nucleic acids to prepare for
release.
“Stage D (4)”
The host cell breaks open (lysing) and
the newly assembled viruses begin to be
released.
V: Bacteriophage Lytic Cycle
“Lysogenic Cycle”
Definition: process by which a virus
embeds its DNA into the DNA of the
host cell and is replicated along with the
host cell's DNA.
Lysogenic cycle is a viral reproduction
cycle in which the virus is dormant until
it enters the lytic cycle.
“Lysogenic Cycle”
What is a “Retrovirus”?
Definition: a virus that contains RNA as
its genetic material instead of DNA.
Viruses cause “Disease”
How: by disrupting the body’s normal
equilibrium. In many viral infections, viruses
attach and destroy certain cells in the body,
causing the symptoms of the disease.
“HIV”
(Human Immunodeficiency Virus)
Definition: retrovirus that destroys white
blood cells called helper T cells and causes
the disease known as AIDS (Acquired
Immune Deficiency Syndrome).
“Influenza”
(Flu or Grippe)
Definition: a highly infectious respiratory
disease.
Your best defense against this virus is to
receive an annual vaccination (according to
the Mayo Clinic).
What is a “Vaccine”?
Definition: a preparation of weakened
or killed pathogens. When injected into
the body, a vaccine sometimes prompts
the body to produce immunity to the
disease.
V: How Vaccines Work
What is “Immunity”?
Definition: the body's ability to destroy
new pathogens.
What are “Antibiotics”?
Definition: compounds that block the
growth and reproduction of bacteria.
DO NOT work on viral infections!
Who is a “Immunologist”?
Definition: a person who
specializes in the immune
system, to study the
mechanism used by the virus
to infect cells.
If a company wants to
develop antiviral drugs, they
would need to ask a research
immunologist.