1. Introduction to VIRUSES
Biology 11
Mrs. Trevelyan

2. Starting with MICROBIOLOGY…
Micro means very small and biology is the study of living things.
Microbes are the oldest form of life on Earth.  They've been here for 3.8 billion years!
Microbes live everywhere. They live, in soil, rocks, air, animals, and even in our colons!
Some microbes are harmful because they cause diseases, but other microbes are beneficial

3. Types of Microorganisms
Viruses (do not belong to a Kingdom)
Bacteria (Kingdoms Eubacteria and Archaeobacteria)
Protists (Kingdom Protista)
Fungi (Kingdom Fungi)

5. Viruses 1. PRESCRIBED LEARNING OUTCOMES and VOCABULARY 2. VIDEO:
Life Sciences: Viruses (20 min)
3. TEXTBOOK PGS
Viruses- pgs

6. VIDEO Life Sciences: Viruses
Discussion Questions ***SEE HANDOUT***
1. What is a virus, and how does it reproduce?
2. How does the body fight a virus? What are antibodies?
3. What was Edward Jenner’s discovery, and how did it lead to the development of vaccines?
4. How does a vaccine work?
5. Who invented the polio vaccine—the first vaccine that didn’t make people sick?
6. How can new viruses emerge?
7. What viral disease affects one in 100 people between the ages of 15 and 49 and is especially prevalent in Africa?
8. What is one way new viruses are being monitored and controlled?

7. Viruses Latin for the for the word “Poison”
A non-cellular particle made up of genetic material and protein that can invade living cells
Genetic material= DNA or RNA
Examples:
influenza (common cold)
HIV (human immunodeficiency virus)
H1N1 (bird flu)
HPV (human papilloma virus) = warts
influenza
HIV

8. Viruses
tobacco mosaic virus
Must infect living cells for reproduction and as such cannot be grown in culture in labs
Have living and non-living characteristics:
Living
Non-living
Has genetic material
But only DNA or RNA, not both
Can reproduce
But needs a host cell to do it
Can mutate
Non-cellular
Can be “killed” (sterilization)
Do not grow, no metabolism

9. Typical Shape and Structure
About 0.2 microns in size, or cm
Shapes: rods, blocks, polyhedrons, and complex forms
Core of genetic material (DNA or RNA)
Surrounded by protein coat (CAPSID)
Some have a lipid ENVELOPE surrounding this

10. Typical Shape and Structure

11. Example: BACTERIOPHAGE
A virus that attacks bacteria!
ACTIVITY: Build your own pet pipecleaner bacteriphage
(A retrovirus has RNA instead of DNA)

12. Virus Reproduction
Use INDIRECT reproduction (a host cell does all the work)
Two types of life cycles a virus may use: LYTIC or LYSOGENIC
LYTIC LIFE CYCLE (fast and destructive ) causes disease = virulent
STEPS:
1. virus attaches to host cell
2. virus inserts its genetic material into host cell
3. viral genetic material remains separate from host cell DNA
4. host cell machinery manufactures viral parts
5. parts assemble inside the cell to form new viruses
6. viruses leaves host cell (explodes= LYSIS) and infect other cells

13. LYTIC LIFE CYCLE
GIZMOS ACTIVITY: VIRUS LYTIC LIFE CYCLE

14. Virus Reproduction LYSOGENIC LIFE CYCLE (delayed = latent) STEPS:
1. virus attaches to host cell
2. virus inserts its genetic material into host cell
3. viral genetic material becomes part of host cell DNA
4. host cell reproduces, making more copies of viral genetic
material as well as its own
5. a STRESS activates the dormant viral genetic material
6. host cell machinery manufactures viral parts
7. parts assemble inside the cell to form new viruses
8. viruses leaves host cell (explodes= LYSIS) and infect other
cells
e.g. Cold Sore Virus
STRESS

15. LYSOGENIC LIFE CYCLE
ASSIGNMENT: Cut and Paste Life Cycles

16. Viruses that cause Human Disease

17. SPREAD of VIRAL INFECTION
The mechanism of spread depends on the type of virus
Some are airborne (via sneezing/coughing etc), others spread through bodily fluids (blood, semen, saliva)
Some only require skin-to-skin contact
ACTIVITY: Spread of Virus Simulation

18. VIRAL SPECIFICITY
Viruses can only invade or infect certain organisms or cells = SPECIFICITY
Most viruses are classified based on the type of host cell they infect
E.g. Tobacco mosaic virus – a virus that attacks tobacco plants and causes a mosaic pattern on the leaves (no smoking while harvesting tobacco!)
For Humans, we often use more general names
E.g. small pox, polio, chicken pox, measles, hepatitis, cold sores, HIV

19. VIRAL SPECIFICITY
Some viruses are even more specific and will only attack specific tissue
E.g. Polio viruses only invade nerve tissue
E.g. hepatitis only occurs in the liver
E.g. mumps attack salivary glands in the mouth
Specificity is determined by the viral glycoprotein spikes (keys) being able to “bind” to the host cell receptors (locks). If they do not fit exactly, no infection will occur.
Virus
Host Cell

20. SYMPTOMS OF VIRAL INFECTION
NEVER use ANTIBIOTICS to treat a VIRAL infection!!!!!

22. How the Body Fights Infection

23. How the Body Fights Infection
The immune system has 3 levels of defence:
1. Primary Line of Defence- involves non-specific physical barriers
Includes skin
Also, mucous membranes and their secretions (think nasal and throat mucus, saliva, wax in ears, vaginal mucus, tears)
Stomach acid also kills most microbes

24. How the Body Fights Infection
2. Secondary Line of Defence- non-specific, attacks any and all foreign objects (virus, bacteria, etc)
includes phagocytic white blood cells (pac-man) that engulf any foreign objects found in the body
Also includes antimicrobial proteins
Involves the INFLAMMATORY RESPONSE
Increased blood flow and migration of phagocytes to the area of infection- usually a wound in the skin
Puss is basically white blood cells
Other blood components such as platelets cause clotting

25. The Inflammatory Response

26. How the Body Fights Infection
3. Tertiary Line of Defence- this is specific to the type of foreign invader
Includes lymphocytes, T-cells and B-cells and antibodies
Antibodies (key) must bind exactly to the antigen (lock)

27. How the Body Fights Infection
Why doesn’t the body always win?
Some viruses MUTATE, changing the shape of their antigens so the antibodies no longer work
Some viruses attack the immune system itself, such as white blood cells
Some viruses reproduce faster than the body can react

28. Eating Boogers may Train you Immune System...
...but it is still pretty gross!

29. The importance of Vaccines

30. Vaccination
Vaccines are available to prevent certain diseases caused by viruses and bacteria (lead to IMMUNITY)
Consists of an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe, its toxins or one of its surface proteins
The agent stimulates the body's immune system to recognize the agent as foreign, destroy it, and "remember" it (= TERTIARY line of defence)

31. The importance of Vaccines

32. The importance of Vaccines

34. The importance of Vaccination
A sample of baby vaccines:
2 months- diphtheria, tetanus, whooping cough, polio, Hib, Hepatitis B, Meningcoccal disease, Pneumococcal disease and rotavirus
4 months- booster shot
6 months- booster shot, flu shot
12 months- the flu shot, Meningcoccal disease, measles, mumps, rubella, pneumococcal disease, chicken pox

35. When people Refuse Vaccination
There are some who are concerned that vaccines can be harmful and are refusing to have their children vaccinated
Others refuse on religious grounds
E.g. Amish communities polio outbreaks
Vaccine-preventable outbreaks:

36. When People Refuse Vaccination

37. Virus Research Project
Because viruses have been in the headlines, data abounds. Viruses impacting people around the world today include avian influenza (bird flu), Ebola, influenza, hepatitis, HIV/AIDS, Marburg hemorrhagic fever, SARS (Severe Acute Respiratory Syndrome), and West Nile virus. Each student is to select a virus to track and must complete a report that includes the following:
• A brief description of the virus and the disease it causes
• A map showing the virus’ *recent* spread
• A chart or graph showing the number of cases over time
• A summary that includes the virus’s impact to date, projected impact in the future, and efforts to stop it
• A list of ways to prevent contracting the virus
A helpful website:

38. In Summary Activity: Section 18.2 Viruses Review Questions
Virus Rap:
Activity: Section 18.2 Viruses Review Questions