Virus Test Review Guide
1. Describe a virus. Give some examples.
Protein sac filled with genetic info (DNA or RNA)
HIV, chicken pox, measles, common cold, whooping cough
2. Why does the term obligate intracellular parasite apply to a virus?
It has to live inside a host cell to replicate and harms the host
3. Distinguish between a retrovirus and a virus. Which is less stable or mutates more?
Retrovirus = RNA and a regular virus = DNA
Retrovirus are less stable and mutate more often (ex. HIV)
4. Draw and describe the lytic and lysogenic reproductive cycles of a virus. Demonstrate how lysogenic can move into the lytic cycle. Identify/label the prophage in the lysogenic cycle.
5. What is a bacteriophage?
Virus that infects a bacterium
6. What is a vaccine? What is the difference between a primary and secondary immune response?
Weakened or dead viral particles that are injected into a person. Primary response occurs with the vaccination. When the body first recognizes the virus as foreign and begins to build antibodies
the body negatively. Secondary response is much stronger and aggressive against the virus because your body already has the antibodies to recognize and fight the virus.
7. Why has there been a concern with using vaccines? What do we know not that may change people’s minds?
Due to Wakefield’s study people believed it may lead to autism. The study was found to be untrue.
8. Why is a virus considered an intracellular parasite?
Same as number 2
9. How big is a virus compared to prokaryotes & eukaryotes? Is it living? What can it infect? Is it species or tissue specific?
Smaller than a bacterium. Non-living. Any other organism from humans, to plants, to monkeys…. Generally it is species & tissue specific but some can mutate and “jump” hosts.
10. How does HIV attack the immune system? Do people die from HIV or AIDS?
HIV hides in white blood cells (specifically helper T cells) and turns the immune system against itself.
People are infected with HIV when it moves into the lytic cycle the symptoms are AIDS related.
11. How does a virus infect a cell? How do receptors play a role?
Uses receptors on the virus and cell surface to trick the cell into letting it in thinking it is safe
12. What does it mean if a virus is latent or dormant?
Lysogenic cycle where it only gets copied when the cell divides. It does not damage the cell. When it flips into the lytic cycle then it will make lots of copies and lyse the cell (burst out)
13. What is the outer protein coat of a virus called? What additional structure can be on the outer surface of some viruses?
If it doesn’t have an envelope it is called a “naked” virus
14. Why can’t a virus reproduce on its own?
A virus needs the enzymes, nucleotides, and “machinery” of a host cell in order to reproduce or copy it’s genetic information
15. What does immune-compromised mean? When would this occur? What are the factors that you can control to avoid this?
Immune system is not working properly, vulnerable, or
suppressed. Sick, unhealthy, not eating properly, not exercising, obese, have another disease like cancer. Eat right, avoid stress, get enough sleep, exercise, etc.
16. What is herd immunity? Why is this important?
Enough of population has been vaccinated so it protects those who haven’t been vaccinated from catching the virus.
17. What is the difference between T and B cell?
T cells recognize friend or foe
B cells make antibodies based on message they receive from T cells
18. Briefly describe these types of viral diseases:
a. Pertussis – whooping cough, inflammation of the lungs,
commonly affects infants and young children
b. Measles – causes fever and red rash on skin, US declared free
of this virus in 2000 but has returned , very infectious
c. Small pox – causes small puss filled bumps on the skin,
injection of cowpox created immunity against this virus
d. Shingles – both shingles and chickenpox are caused by the
lysogenic replication cycle of this virus and usually occurs years after a person has had the chickenpox
e. Polio – effects the spinal cord leaving many infected
individuals paralyzed, infection rate dropped by 99% when vaccine was introduced in 1955 by Jonas Salk
19. What are the lines of defense within the immune system?
Surface barriers – skin, mucous
Internal Defenses – fever, inflammation, & phagocytes B cells & T cells
20. What is the difference between innate and adaptive immunity?
Innate immunity = natural lines of defense like surface barriers and internal defenses
Adaptive Immunity = lymphocytes aka B cells (humoral) and T cells (cell-mediated)
21. What is the difference between antigen and an antibody?
Antigen = Identifying protein on the surface of a cell or pathogen
Antibody = released by B cells to attack antigens. Trap invading viruses or bacteria in large clumps (agglutination)
22. What role do macrophages play in the immune system?
Phagocytes that “eat” or engulf foreign material in body
23. What is the difference between helper T cells and killer (cytotoxic) T cells?
Helper T cells “help” B recognize invaders & stimulate the B cells to grow and make antibodies
Killer or cytotoxic T cells destroy the pathogen directly – causes infected cell to lyse or go thru apoptosis
24. What ailments or diseases are triggered when the immune system doesn’t work properly?
Allergies overreacting to certain stimuli and
• Diabetes –attacks insulin producing cells in pancreas
• Rheumatoid Arthritis –attacks connective tissue around
joints
• Multiple Sclerosis (MS) – destroys functions of brain and
spinal cord neurons
