Transcript Virus Replication PPTx

AKA the things that make us sick!
The Virus

Viruses are tiny, non-living particles (NOT
cells!) that infect living cells
› Cannot reproduce on their own
› Do not grow or develop
› Do not use energy
Parts of a Virus
Protein shell called a
capsid
 genetic material (DNA
or RNA)
 Envelope made of
stolen cell membrane
 Glycoproteins that
attach to cells
(handshake)

Parts of a Virus
The virus we looked at
yesterday is called a
bacteriophage
 It has the same
structural
characteristics, but
different names

Different Forms of Viruses
Viral Replication
Viruses confuse cells, turning them into
virus factories:
1.
2.
Virus finds and attaches
to a cell by matching
glycoprotein receptors
(handshake)
DNA or RNA from virus
enters the cell
Viral Replication
3. Viral DNA or RNA is copied many times; cell is
fooled into reading these new instructions
4. New viral structures are manufactured
5. New viruses burst out of the cell, killing it
Two Types of Viral Infection
1.
2.
Lytic Infection – virus enters a cell and quickly
makes copies, causing lysis of the cell
Lysogenic Infection – a virus “hides” its DNA
inside a host cell and lies dormant
› Viral DNA is copied each time the cell divides
› Will eventually turn lytic
Viral Specificity
Viruses are very
specific – infect only
certain cells
› Ex: cold virus infects
respiratory cells
The handshakes have to match!
Example 1 - Influenza
Attacks and kills
respiratory cells,
causing flu
symptoms
 Spreads fast, is
copied quickly –

lytic!
Example 2 - HIV
Human Immunodeficiency
Virus attacks and kills cells of
the immune system
 Takes years to actually
cause illness –

Lysogenic!

Death of immune cells leads
to AIDS (acquired immune
deficiency syndrome)
Video
Vaccines

Vaccines are used to give immunity
against viral infection
› Contain damaged/weakened form of a virus
› The immune system can then recognize and
destroy the real virus if it ever enters the body
There is no scientific
evidence
whatsoever that
autism is linked to
vaccination!