5. Viruses
A virus is a small infectious particles containing genetic
material (DNA or RNA) within a protein capsule (capsid).
6. Viruses
Viruses reproduce by inserting their genetic material
into host cells and "taking them over".
The general name given to a single virus particle that is
not infecting a cell is "virion".
7. Viruses
A virus is an obligate parasite; it requires a host
cell to reproduce.
8. Viruses
They are responsible for many diseases.
Epidemic: Large-scale disease outbreak in a region.
Pandemic: Multi-region or global disease outbreak.
AIDS
9. Viruses
There are many different ways viruses can be
transmitted:
Disease Transmission Method
rabies bites (saliva blood)
HIV body fluid exchange
– excluding saliva
influenza, chicken pox, airborne/direct contact
common cold
measles, mumps direct contact
10. Viruses
They are non-living, thus they do not fall into any taxa.
Which properties of living things do they not have?
11. Differences Between Viruses and Cells
Life cycle:
How can
something
without life
have a "life"
cycle?
Genetic
material:
Viruses contain
RNA or DNA
Organelles: enclosed by
None. protein, not a
membrane.
12. Differences Between Viruses and Cells
Size:
Viruses are
much
smaller
than cells.
Metabolism:
Viruses do not
metabolize
(no
cytoplasm).
13. Viruses
Can be classified into orders/families/genera/species:
- size
- shape
- genetic material
- single-stranded or
double-stranded
DNA/RNA
- host cells
A bacteriophage (phage) is a virus that infects bacteria.
20. Infectious Cycles
Lysogenic cycle: Host cell survives, but when it divides
the virus DNA/RNA is also duplicated.
Viral
DNA/RNA
Bacterial
DNA
A) Attachment
& Entry
21. Infectious Cycles
Lysogenic cycle: Host cell survives, but when it divides
the virus DNA/RNA is also duplicated.
Provirus
B) Integration – viral nucleic acid
becomes part of host nucleic acid
22. Infectious Cycles
Lysogenic cycle: Host cell survives, but when it divides
the virus DNA/RNA is also duplicated.
C) Multiplication of genome
24. A) Attachment bacterial B) Insertion
virus
DNA - Virus injects its
viral DNA nucleic acid
into host
bacterial host cell cell
E) Lysis &
Release
C) Replication
- The host’s
D) Assembly metabolism
- New viral particles replicates the viral
are assembled RNA/DNA
25. Infectious Cycles
The 2 cycles are
interchangeable
and a virus may
be in lysogeny
for many years.
26. Infectious Cycles
Sometimes newly formed viruses take sections host
DNA (and host genes) with them.
Transfer of genes using a virus is called transduction.
31. Viruses - Benefits
We can now craft viruses that contain beneficial genes
or drugs within their capsids (called viral vectors).
32. Viruses - Benefits
These vectors enter the target cells and deliver their
payload:
Vector Contents Application
Drugs Ex. Chemotherapy for
cancerous cells.
Copies of beneficial genes Gene therapy (replacement
or addition of new or better
genes).
Novel (new) genes Creation of GMOs
(genetically modified
organisms).
33. Viroids
A viroid is an infectious piece of RNA. It does not code
for anything and has no protective structure like a
capsid.
