1. Viruses

2. 1 nanometer (nm) = one billionth of a meter
What is a Virus?
1 nanometer (nm) = one billionth of a meter
100 nm
eukaryotics cells 10, ,000 nm
viroids nm
viruses nm
prokaryotics cells ,000 nm
prion 2-10 nm
Virus: A biological particle composed of nucleic acid and protein
Intracellular Parasites: organism that must “live” inside a host

3. Are viruses alive? No Yes Not made of cells or organelles
Can’t reproduce on own
Don’t metabolize energy
Don’t perform cellular processes
Reproduce
Have nucleic acid
Adapt to surroundings
Have organization

4. All Have:
1) Capsid: coat of protein that surrounds nucleic acid
2) Nucleic Acid: RNA or DNA
Some Have:
Tail Fibers: Used for attachment (not legs)
Shape & size varies
Virus
Parts

5. Virus Video

6. Viral Replication
Bacteriophages (viruses that attack bacteria) are often studied
Replication is similar with many animal viruses
Two “life” cycles: Lytic & Lysogenic
Dozens of phage viruses attacking an E. coli bacteria cell
The bacteria cell is destroyed and new viruses escape

7. The Lytic Cycle 1st Step: Attachment Virus lands on cell membrane
Virus attaches to a cell receptor
Virus acts as key; receptor acts as lock
No attachment = No infection

8. The Lytic Cycle 2nd Step: Entry Virus enzyme weakens cell membrane
endocytosis
2nd Step: Entry
Virus enzyme weakens cell membrane
Genetic material (DNA or RNA) enters host cell

9. The Lytic Cycle 3rd Step: Replication
Virus DNA/RNA uses ribosomes to make virus proteins
Virus proteins created by transcription/ translation
transcription
translation
Viral DNA
Viral RNA
Viral Proteins

10. The Lytic Cycle 4th Step: Assembly
New virus proteins are assembled in the cytoplasm

11. The Lytic Cycle 5th Step: Release
Virus enzyme causes cell membrane lyse (burst)
Viruses are released to find new host
Cycle repeats

12. All stages on one slide Attachment Entry Replication & Assembly
Release

13. Review
True or False: All viruses have a capsid, nucleic acid, and tail fibers.
List 3 reasons why viruses may be living? Nonliving?
What is the virus capsid made from?
What type of organism do phages infect?
In order list the stages of the lytic/lysogenic cycles.
In which stage…
does the host cell explode?
are virus proteins built to make new viruses?
is a provirus created?
does a virus connect with the host cell’s receptors?
Which two objects make up a provirus?
Which virus “life” cycle is considered the most harmful? Why?

14. The Lysogenic Cycle

15. The Lysogenic Cycle 1st step: Attachment = Same as lytic cycle
2nd Step: Entry = Same as lytic cycle

16. The Lysogenic Cycle 3rd step: Replication Provirus Created
Virus DNA combines with cell DNA
Infected cell divides by mitosis and copies the provirus
Each new cell will contain the provirus
Provirus can remain dormant
Virus DNA
Pro-virus
cell DNA
Pro-virus
Pro-virus

17. The Lysogenic Cycle 5th Step: Release 4th Step: Assembly:
Same, except many cells burst releasing many more viruses
4th Step: Assembly:
Same, except many new viruses are assembled in many cells

18. The viral DNA become active and starts making new viral proteins
The infected cells burst…releasing the new viruses

19. Reverse Transcription
Retroviruses
Type of RNA virus
Contain enzyme called “reverse transcriptase”
Steps
1) Virus RNA enters host cell
2) Reverse transcription changes the virus RNA into DNA
3) Virus DNA fuses with cell DNA (provirus created)
Viral DNA lays dormant
4) Infected cell divides and spreads the virus
5) Eventually, the viral DNA becomes active in many cells
Viral DNA  Viral RNA  Viral proteins
Normal Transcription
DNA  RNA
Reverse Transcription
RNA  DNA

20. How is HIV contracted? High risk activities: Low risk activities:
1) Sex (oral, vaginal, anal)
2) Sharing needles (tattoos, piercings, drugs)
Low risk activities:
3) Mother to child in womb
4) Breast milk
5) Blood transfusions

21. HIV Prevention
100% Effective: Abstinence (not participating in sexual acts)
If sexually active: Latex condoms are the only forms of birth control that prevent STDs and pregnancy
If drug user: Change needles

22. What is AIDS? Acquired Immunodeficiency Syndrome AIDS results when:
1) Amount of T-cells drop (200 T-cells per 1mm³ blood)
2) Multiple symptoms/infections appear
Rash, fever, headache, sore throat, swollen lymph nodes
Therefore, the HIV virus causes the disease AIDS by killing your T-cells

23. What is AIDS? Acquired Immunodeficiency Syndrome AIDS results when:
1) Amount of T-cells drop (200 T-cells per 1mm³ blood)
2) Multiple symptoms/infections appear
Rash, fever, headache, sore throat, swollen lymph nodes
Therefore, the HIV virus causes the disease AIDS by killing your T-cells
Gender of those living with HIV (2003)

24. What is AIDS? Acquired Immunodeficiency Syndrome AIDS results when:
1) Amount of T-cells drop (200 T-cells per 1mm³ blood)
2) Multiple symptoms/infections appear
Rash, fever, headache, sore throat, swollen lymph nodes
Therefore, the HIV virus causes the disease AIDS by killing your T-cells
2009: New Infections
MSM: Men having sex with men
IDU: Intravenous drug users (share needles)
MSM/IDU: Men who share needles and have sex with men

25. Female Transmission of HIV
What is AIDS?
Acquired Immunodeficiency Syndrome
AIDS results when:
1) Amount of T-cells drop (200 T-cells per 1mm³ blood)
2) Multiple symptoms/infections appear
Rash, fever, headache, sore throat, swollen lymph nodes
Therefore, the HIV virus causes the disease AIDS by killing your T-cells
Female Transmission of HIV
(2006)

26. AIDS Quilt
3ft x 6ft quilt panel
can be created as
a memorial tribute

27. AIDS Quilt
Panels from across
the world are
sewn together

28. Panels travel around the world to help remember and raise awareness
AIDS Quilt
Panels travel around the world to help
remember and raise awareness

29. AIDS Quilt
Over 44,000 panels
exist today

30. Review Name the enzyme found within retroviruses.
The picture shows the normal steps of protein synthesis. Fill in the question marks with the words: Translation, Protein, Transcription, DNA
The picture below shows the steps of a retrovirus. Fill in the question marks with the words: viral RNA, transcription, translation, reverse transcription, viral DNA