Name
Date
20 – Viruses & Prokaryotes
20.1 Viruses
Discovery of Viruses
- Dmitri Ivanovski – realized an
(substance) was causing disease in
(Tobacco Mosaic disease)
-
Martinus Beijerink – determined small particles cause the disease, which he called
(Latin for
)
-
Wendell Stanley – isolated
o Determined that viruses are
Structure
- Nonliving particles made of
) and sometimes
of the Tobacco Mosaic Virus
because living things cannot be
,
(membrane)
(
-
Many
, but can only be seen with an
-
Parts of a Virus:
o Capsid –
surrounding the virus

is found within capsid
 Some viruses have an additional
around capsid (such as
)
o Capsid proteins –
on surface, used
to
(host)
 Proteins bond to specific
,
allowing most viruses to only infect
-
Viruses can use either
as their genetic material
Infections
- Viruses can only ‘reproduce’ by
and using it to make more
-
(Eukaryote infections are very similar)
Two methods of
o Bacteriophage –
Lytic Infection:
- Virus attaches to cell at
- Virus
or
into cell
instructs the cell to make
that destroy the
- Cell is used to make thousands of
- Viral DNA is used to make
for the new viruses
- New viruses are
- Cell
releasing the newly made viruses, which will infect more cells
Lysogenic infections:
- Virus
or
-
into cell
DNA
o Prophage –
, but it is
into the cell’s DNA
that has been inserted into cell’s DNA
o Provirus -
Viral DNA will be
so all
-
The prophage
-
Certain
o
RNA Viruses
- Common Cold:
o Virus inserts its
o
o Cell
o Process takes
-
along with the cell’s DNA
are also infected
,
(unused) for a long time
trigger the viral DNA to begin
begins and new viruses are made
use RNA as their genetic information,
are made, which are then used to build more
and viruses infect more cells
HIV: Human immunodeficiency virus
o Virus that causes
o
– virus inserts
 DNA copy is inserted into
o Similar to
o Once activated,
o Virus will begin to destroy the
(AIDS)
, which is used to make a
– viral DNA may remain
for long periods of time
is used to make copies of the virus
Viral Disease
- Diseases are caused when viruses
- Disease Mechanisms:
o Viruses
certain cells in the body, causing
associated with those cells/systems
 Poliovirus attacks
, causing
o Viruses change the
causing
- Preventing disease:
o
– washing hands to prevent virus from
o
– inactive viruses used to build up a person’s
particular virus
- Treating disease:
o Cannot use
(only work on bacteria – bio=living)
o Some
have been developed to prevent virus from
in cells, sometimes
to a