Download Viruses 1-1

Viruses
1-1-1
1 – main characteristic
1 – surprising fact
1 – question
Viruses
What’s a Virus?
1. Viruses are tiny particles that can invade living cells.
Because viruses are not cells they are non-living and can
not perform all the functions of living cells.
For example, they cannot take in food or get rid of
wastes. In fact, about the only life function that viruses
share with cells is reproduction.
2. Viruses can only reproduce (multiply) when they
are inside a living cell.
3. The organism that a virus enters is called the
host. A host is a living organism that provides a
source of energy for a virus or organism.
4. Organisms that live on or in a host and cause
harm to the host are called parasites.
• Almost all viruses act like parasites because they
destroy the cells in which they multiply.
When you have a cold, are you the host or a
parasite?
How Viruses Multiply
The Structure of a Virus
5. A virus is a piece of genetic material (DNA
or RNA) covered by a protein called the
protein coat, that infects and reproduces
only in a living cell.
Genetic material
(DNA or RNA)
Protein coat
The Size of a Virus
6. Viruses are so small that they can only be
seen with very powerful microscopes. They are
about 100X smaller than a typical bacterium.
They are measured in nanometers (nm) which
are 1 billionth of a meter! (1/1,000,000,000; 1/109)
Virus
How Big is a ….?
Viruses come in many sizes and many
shapes.
Viruses are not included in the classification system we
studied and are not named using binomial nomenclature.
Can you tell me why?
Viruses are often named for the diseases they cause or
the organ or organism they infect.
rabies virus – causes the
disease rabies
adenovirus – infects
adenoid tissue
bacteriophage – is a virus
that infects bacteria
Viral Diseases
7. Viruses can cause diseases in plants,
animals, fungi, bacteria and protists.
8. There are no antibiotics to cure viral
diseases. But some viral diseases can be
prevented by vaccines.
A vaccine is made from damaged virus
particles that can’t cause disease anymore.
9. Edward Jenner, an English
doctor, is credited with developing a
vaccine in 1796. Jenner developed
a vaccine for smallpox, a disease
that was greatly feared, even into
the twentieth century.
Jenner noticed that people who
milked cows and came down with a
disease called coxpox didn’t get
smallpox. He prepared a vaccine
from the sores of milkmaids who
had cowpox. When he injected it
into healthy people, the cowpox
vaccine seemed to protect them
from smallpox.
Viral Diseases in Humans
Disease
Affected Body
Part
Vaccine
Aids
Immune system
no
Chicken pox
Skin
yes
Common cold
Respiratory system
no
Influenza or flu
Respiratory system
yes
Measles
Skin
yes
Mumps
Salivary glands
yes
Polio
Nervous system
yes
Rabies
Nervous system
yes
smallpox
Skin
yes
The good thing about viruses is…
10.Viruses are used in gene therapy.
Scientists take advantage of a virus’s ability to enter a host cell.
They add important genetic material to a virus and then use the
virus as a messenger service to deliver the genetic material to the
cells that need it.
This technique has been used successfully for treating cystic
fibrosis. Researchers are hoping to use similar techniques for
sickle-cell anemia and cancer.
Viruses
1-1-1
1 – main characteristic
1 – surprising fact
1 – question