1. Viruses What are the characteristics of living organisms?
Living things…
are made of cells
grow and develop
reproduce
respond to their environment
adapt to their environment
obtain and use energy
produce wastes 1

2. Magnified image of a virus
Viruses
Magnified image of a virus
Image of an animal cell
viruses on their own can be considered lifeless chemicals, unless ……? 2 2

3. Viruses
Answer
viruses are not considered to be living organisms because: 3 3

4. Typical Viral Stucture4 4

5. Viral Capsids
Examples:

6. Viral Classification Viruses are generally classified by: 1.
host range (types of cells that the virus can infect)
examples: a) cold virus
b) rabies
c) HIV
d) bacteriophage 2.
size and shape of the capsid
type genetic material
(human respiratory cells)
(nerve cells in dogs, rodents, humans) 6

7. Viral Size very small, measured in units called nanometres (nm)
1nm = 1X10-9 m
(billionth of a metre)
size ranges from nm 7

8. Viral Replication
Process by which the virus and its genetic material are duplicated before its host cell divides
4 Basic Steps
Virus chemically recognizes a , attaches to it, and enters it (either the whole virus or only its genetic material – for some viruses, this can be DNA or RNA).
Newly incorporated viral DNA or RNA directs the host cell to (nucleic acids, enzymes, capsid proteins, and other viral proteins)

9. These viral components are brought together and assembled into
The newly formed virus particles are released from the This is called
Steps 1 through 4 = and may be completed in as little as minutes and produces hundreds of new virus particles.

10. Lysogenic Cycle
Some viruses (e.g., that infect bacteria or cause cancer) may coexist with a cell and be carried through The virus’ genetic material is integrated into that of the host cell, however instead of , this newly replicated genetic material is . The virus in this case is in a dormant state called and may be activated by stimuli such as . Once activated, the viruses trigger the .

12. Viruses
&
Human Health‏
June 23, 2009

13. cause cells to become cancerous
Viral diseases are difficult to treat because:
ex. a) Herpes Simplex Virus I (HSV I)
(cold sores)
b) HIV
Some viruses are
cause cells to become cancerous
onco = tumour
(AIDS)
(genital warts)
(cervical cancer)
ex. Human Papiloma Virus (HPV)
April 14, 2019
SBI3C 13

14. Protection Against Viral Diseases
 vaccines:
people are given a dead or weakened form
of the virus
builds up an army of WBC’s & antibodies to
kill the living virus immediately before it
can reproduce
ex. polio vaccine,
hepatitis B vaccine
Antibiotics
antiviral agents:
ex. Valtrex – helps heal and decrease pain
(herpes)
SBI3C

15. Viral Uses In Medicine 1. Viral Vectors
Viruses can be used for gene therapy as “carriers”
Viral core is removed &
desired human gene is added
Virus is mixed with living
cells
Virus attaches to human host
cell & injects the human gene
i.e. acts like a microscopic
hypodermic needle
(Dr. John Bell) OHRI (Ottawa Health Research Institute): University of Ottawa professor
success with mice injected cancer cells : also trials in humans that didn’t respond to conventional cancer treatments (chemotherapy & radiation) tumours receded wthin weeks
cancer cells give off hormones that inhibit immune response
also found that viruses stimulated response & person was immune to that form of cancer for life 15

16. SOME EXTRA INFO ON HIV…

17. Worldwide HIV Distribution
Note: Total exceeds 100 percent due to rounding.
Source: UNAIDS, 2006 Report on the Global AIDS Epidemic, 2006.

18. Structure of HIV