Transcript 11. 2 Viruses - Father Michael McGivney Catholic Academy

11.2 Viruses
Characteristics of Viruses
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are _______ since they have __
___________ and are not classified in
any kingdom of living things
have no organelles, _______ or
__________ and rely upon other living
organisms to reproduce
Characteristics of Viruses
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consist of DNA or RNA strands
contained within a protective protein
coat called a _______
the capsid protects the virus from
attack by host cells and is a means by
which viruses are classified
Characteristics of Viruses
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shapes of capsids: polyhedral, spherical,
cylindrical, polyhedral with a protein tail
Exs.
Characteristics of Viruses
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Viruses are also classified by the type of
________ they contain, DNA or RNA
and by the types of _______ they cause
DNA and RNA Viruses
1) DNA viruses: ____ _____ and follow the lytic cycle
 able to be detected and destroyed by the human
immune system
2) RNA viruses: most virulent and can remain
__________ for a period of days or months or even
years
 Follow the ____________ but once they are active
in a host they can be detected by the immune
system
 Cause diseases like _______, rabies and ________
Viral Reproduction
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There are 2 types of viral reproduction :
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1) Lytic Cycle
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2) Lysogenic Cycle
Lytic Cycle
1) virus attaches to the _______ of the host cell
2) virus injects its nucleic acid into the bacterial
cell and takes over the host mRNA
3) the host cell replicates the viral DNA
4) new virus particles are then _______ in the
cell and then released through cell ______
5) the new particles attack neighbouring cells
Lysogenic Cycle
1) the __________ becomes attached to
cell wall
2) viral DNA is _______ into the host cell
3) viral DNA inserts itself into the host cell
DNA by _________
4) when the host cell reproduces its
genetic content, the ________ are also
replicated
Lysogenic Cycle (cont’d)
5) for many generations, there are no
active viral particles produced
6) occasionally, the viral DNA will become
active in a host cell (_______ which
triggers reproduction)
7) bacterium lyses, releasing new viruses
8) phages carry genes from host cell to
neighbouring cells
Retroviruses
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When an RNA virus enters a host cell it
must first convert its ___ to ____
This is done using a special enzyme
called ______________, which the RNA
virus carries
It is now able to _____ the viral ___
into the host genome and follows the
_________ cycle