2. Viruses
Viruses are not classified in any kingdom. They show no traits like the living things in the 6 kingdoms we will be studying.
WHAT IS A VIRUS?

3. vs A. General Characteristics
1. A virus (aka virion) is an infectious agent made up of – nucleic acid (DNA or RNA), wrapped in protein coat
a. they have no nucleus, no organelles, no cytoplasm or cell membrane – non-cellular particle
b. viruses have either – DNA or RNA, but not both vs

4. Ex: HIV, flu (influenza), cold
c. viruses with RNA that transcribes into DNA (using enzyme reverse transcriptase) are called – retroviruses
Ex: HIV, flu (influenza), cold
RNA viruses have a high rate of mutations – replication of RNA does not involve proofreading step (as in DNA replication)
HIV Infected Cell
(This is the reason why HIV is so incurable.)

5. 2. Viruses are - parasitic - organism that depends
2. Viruses are - parasitic - organism that depends entirely upon another living organism (host) for its existence in such way that it harms that organism.
A flea is a parasite to a dog and is harmful to the dog.

6. 1. Bacteriophage—viruses that infect a bacteria
B. Examples
1. Bacteriophage—viruses that infect a bacteria
Capsid (protein coat)
2. Flu (influenza), HIV
DNA
Tail fibers
Envelope—has marker proteins + carbs derived from host cell
RNA
Capsid

7. Bacteriophage—a virus that infects bacteria (bacteria is the host)
Capsid
Nucleic Acid
Bacteriophage—a virus that infects bacteria (bacteria is the host)

8. C. Replication (reproduction): How a virus spreads.
***A virus CANNOT reproduce by itself—it must invade a host cell and take over its activities.
1. Virus (bacteriophage) invading a bacterium (E. coli)
Virus uses what it needs from cell + makes more virus
Lytic = split
Virus attaches
to cell
DNA of virus enters cell
Cell bursts, new viruses are released
Cell divides, replicating DNA of virus
Virus DNA becomes part of cell’s DNA

9. 2. During Lysogenic Cycle, it is possible for viral DNA to separate
2. During Lysogenic Cycle, it is possible for viral DNA to separate from host cell DNA and cause cell to enter Lytic Cycle and replicate new viruses
Virus uses what it needs from cell + makes more virus
Lytic = split
Virus attaches
to cell
DNA of virus enters cell
Cell bursts, new viruses are released
Cell divides, replicating DNA of virus
Virus DNA becomes part of cell’s DNA

10. Lytic Cycle of a Bacteriophage
rapid replication of the virus, ending in cell lysis (or death). More phages are released to infect other cells

11. Lysogenic Cycle of a Temperate Bacteriophage
the virus stays within the cell until certain environmental triggers cause it to enter the lytic cycle

12. Warm-Up Get out a spare sheet of paper. YOU MAY NOT USE NOTES!!!!!
What is a Bacteriophage?
Why are Retroviruses so hard to kill? What is an example of a Retrovirus?
Describe the Lytic and Lysogenic Cycles.

13. Virus DNA becomes part of cell’s DNA
3. Virus invading an animal cell: Ex: HIV invading human cell
Virus DNA becomes part of cell’s DNA
Envelope of HIV contains marker proteins + carbs derived from host cell
Virus particle enters human cell by endocytosis
New virus buds off
RNA replicates

14. Ex: the rabies virus only infects brain or nervous cells
4. Capsid proteins of a virus bind to receptors on cell surface and “trick” cell into allowing it inside.
Because of this fit between virus and cell receptors, most viruses are specific for cells they infect.
Ex: the rabies virus only infects brain or nervous cells
Receptor Sites
Virus
Cell

15. Human Immunodeficiency Virus

17. D. Importance: a. Causes disease—pathogenic
1. Harmful
a. Causes disease—pathogenic
Disease producing agent—pathogen
b. Human Diseases:
DNA: chicken pox, mono, cold sores, genital herpes, warts, hepatitis, smallpox
RNA: cold, influenza, polio, AIDS, rabies, Ebola
c. Viruses disrupt the body’s normal equilibrium/balance (homeostasis)
d. Viruses can be prevented with vaccines, but NOT treated with antibiotics.

18. 2. Beneficial
a. genetic engineering – harmless virus carries good genes into cell

19. Gene Therapy

20. Virus Living Cell Genetic material (DNA or RNA) + capsid
Cell membrane, cytoplasm, genetic material, organelles
Structure
Copies itself only inside host cell
Cell division --Asexual or Sexual
Reproduction
DNA and RNA
Genetic Material
DNA or RNA
Growth and Development NO
YES
Obtain and Use Energy NO
YES
Response to Environment
YES NO
Change over time
YES
YES

22. Are viruses living? NON - LIVING TWO
How many characteristics of life do viruses possess?
TWO
*contains Genetic Material
*change over time
Are viruses living?
NON - LIVING

27. Warm-up Describe the structures of the HIV virus to the right 
2. Are all viruses bad? If not, explain a positive use for Viruses
3. After you are given a cell and surface marker find your match and go visit Ms. Lust for some “medicine”.