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3. BACKNEXT We have all gotten viruses… from bacteria, plants to animals. Viruses cause colds, flu, warts and diseases such as measles, AIDS and cancer. AND not all viruses are harmful to humans. BUT not all viruses cause diseases, Introduction – Structure – Replication – Virology – Medicine - Review

4. BACKNEXT WHAT IS A VIRUS? Introduction – Structure – Replication – Virology – Medicine – Review

5. BACKNEXT Introduction – Structure – Replication – Virology – Medicine - Review A VIRUS is either DNA or RNA, that is protected by a protein coat called a CAPSID. DNACAPSID VIRUS

6. BACKNEXT Why are some viruses harmful? Introduction – Structure – Replication – Virology – Medicine - Review Virus invades cell Virus forces cell to make copies of virus Eventually so many copies are made, the cell explodes, releasing all of the new viruses When your cells make viruses instead of operating normally, YOU get sick

7. BACKNEXT DISEASEVIRUSES AIDSHIV Wart Herpes Simplex Virus FluInfluenza MeaslesMorbillivirus. CancerHepatitis B Introduction – Structure – Replication – Virology – Medicine - Review Examples of some viral diseases:

8. BACKNEXT Who do viruses infect? Viruses infect Bacteria –These viruses are called bacteriophages Viruses infect Plants –One example is the Tobacco Mosaic Virus Viruses infect Animals –One example is the common cold Viruses usually infect a specific host including: Introduction – Structure – Replication – Virology – Medicine - Review

9. BACKNEXT Let’s look at the Defining Properties of Viruses Viruses are parasites that invade cells Viruses have either DNA (Deoxyribose Nucleic Acid) or RNA (Ribonucleic Acid) Viruses direct the synthesis of new virus within a host cell. Newly made viruses infect other cells. Introduction – Structure – Replication – Virology – Medicine - Review

10. BACKNEXT Cell Biology Let's review a little cell biology since viruses cannot multiply without the help of cells. The viruses enter the cell and forces the cell to make more viruses. The cell has three main zones: Introduction – Structure – Replication – Virology – Medicine - Review nucleus membrane cytoplasm Cytoplasm – this is the “factory” where biochemical reactions occur. Membrane – this double layer protects the cell and allows the cell to communicate with the outside environment. Nucleus – this holds the DNA or genetic information about the cell.

11. BACKNEXT DNA/RNA DNA, deoxyribonucleic acid, is the double-stranded molecule that encodes genetic information (e.g. your hair color, height, etc.) in the nucleus of cells. The complete set of DNA in a cell is called the genome. RNA, ribonucleic acid, is typically single stranded so that it can be read to make proteins. Introduction – Structure – Replication – Virology – Medicine - Review DNA or RNA code for genes that defines who we are.

12. BACKNEXT How small is a virus? Introduction – Structure – Replication – Virology – Medicine - Review

13. BACKNEXT If a cell was the size of your classroom, then an average virus would be the size of a softball. Viruses range in size from 20 nanometers (nm) – 250 nanometers (nm) 1 nm = 0.00000004 inches 10 -5 m 10 -6 m 10 -7 m 10 -8 m 10 -9 m 10 -10 m 0 m viruses animal cells bacteria proteins atom Go five more feet!

14. BACKNEXT Helical Capsids Helical capsids are rod- like structures with the RNA in the center of the helix. A helix is made by stacking repeating units in a spiral. RNA protein coat Introduction – Structure – Replication – Virology – Medicine - Review

15. BACKNEXT Tobacco Mosaic Virus Tobacco Mosaic Virus (TMV) is an example of a virus with a helical structure. Protein subunits wrap around the spiraling RNA strand. Introduction – Structure – Replication – Virology – Medicine - Review This image taken using an Electron Microscope

16. BACKNEXT Adenovirus Introduction – Structure – Replication – Virology – Medicine - Review Adenoviruses cause diseases like pink-eye or the common cold

17. BACKNEXT Bacteriophage Introduction – Structure – Replication – Virology – Medicine - Review Bacteriophage is a virus that infects bacteria.

18. BACKNEXT Enveloped Viruses Introduction – Structure – Replication – Virology – Medicine - Review Enveloped viruses are viruses which have a membrane coat surrounding the protein coat or capsid. These viruses are common in animal viruses, but are uncommon in plant viruses. Herpes Simplex Virus. A membrane (made of proteins) surrounds the capsid (also made of proteins) which surrounds the viral DNA.

19. BACKNEXT How do viruses replicate? Introduction – Structure – Replication – Virology – Medicine - Review

20. BACKNEXT Replication Phases V - Release -Assembly of virus DNA and protein coat into whole new viruses -Leaving the cell http://www.cat.cc.md.us/courses/bio141/lecguide/unit2/viruses/adlyt.html Phase I Phase II Phase IV Phase VPhase III Introduction – Structure – Replication – Virology – Medicine - Review I, II, III - Viruses enter cell -Attachment to cell membrane -Penetration inside cell -Losing virus protein coat IV - Replication -Tricks cell into making more viral DNA -Tricks cell into making viral protein coat

21. BACKNEXT The concept of a virus as an organism challenges the way we define life: *Viruses do not breathe. *Viruses do not metabolize. *Viruses do not grow. *However, they do reproduce. Introduction – Structure – Replication – Virology – Medicine - Review

22. BACKNEXT Are Viruses Living? Introduction – Structure – Replication – Virology – Medicine - Review Create a table where one column represent properties of living organisms and the second column represent properties of a virus. Properties of Living Organisms Properties of Viruses Breathes (respires)Doesn’t breathe MetabolizesDoesn’t metabolize GrowsDoesn’t grow Reproduces

23. BACKNEXT Viruses Can Help Cells, Too Introduction – Structure – Replication – Virology – Medicine - Review - Since viruses can transport DNA and RNA into cells, scientists are exploring Gene Therapy - In Gene Therapy, viral genetic material is replaced with new DNA - In time, this could be used to cure genetic diseases. Currently we have no cure for these types of illnesses

24. BACKNEXT Common Viral Diseases Unlike with bacterial diseases, there are currently no medications that can cure viral infections. - Viruses, Bacteria, and Your Health

25. BACKNEXT The End! And Review Viruses are very simple: a shell containing either DNA or RNA. They infect by hijacking cells’ machinery to force them to make more viruses. Viruses are tiny, even compared to a cell. Some viruses may prove useful in gene therapy as natural carriers of DNA that was specially designed to be good for a particular reason. Introduction – Structure – Replication – Virology – Medicine - Review

26. BACKNEXT The End Introduction – Structure – Replication – Virology – Medicine - Review