1. VIRUSES!

2. Introduction – Structure – Replication – Virology – Medicine - Review
CONTENTS
1. Introduction
4. Virology
2. Virus Structure
5. Virus and Medicine
3. Virus Replication
6. Review
Introduction – Structure – Replication – Virology – Medicine - Review

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

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

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

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

7. Examples of some viral diseases:
VIRUSES
AIDS
HIV
Wart
Herpes Simplex
Virus
Flu
Influenza
Measles
Morbillivirus .
Cancer
Hepatitis B
Introduction – Structure – Replication – Virology – Medicine - Review

8. Introduction – Structure – Replication – Virology – Medicine - Review
Who do viruses infect?
Viruses usually infect a specific host including:
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
Introduction – Structure – Replication – Virology – Medicine - Review

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

11. Introduction – Structure – Replication – Virology – Medicine - Review
Helical Capsids
RNA
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.
protein coat
Introduction – Structure – Replication – Virology – Medicine - Review

12. Introduction – Structure – Replication – Virology – Medicine - Review
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.
This image taken using an Electron Microscope
Introduction – Structure – Replication – Virology – Medicine - Review

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

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

15. Introduction – Structure – Replication – Virology – Medicine - Review
Enveloped Viruses
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.
Introduction – Structure – Replication – Virology – Medicine - Review

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

17. Introduction – Structure – Replication – Virology – Medicine - Review
Replication Phases
I, II, III - Viruses enter cell
Attachment to cell membrane
Penetration inside cell
Losing virus protein coat
Phase I
IV - Replication
Tricks cell into making more viral DNA
Tricks cell into making viral protein coat
V - Release
Assembly of virus DNA and protein coat into whole new viruses
Leaving the cell
Phase II
Phase III
Phase V
Phase IV
Introduction – Structure – Replication – Virology – Medicine - Review

18. Introduction – Structure – Replication – Virology – Medicine - Review
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

19. A Brief History of Virology
1898
Martinus Beijerinick work on TMV
Freidrich Loeffler & Paul Frosch work on foot-and-mouth disease in cattle
Bacteriophages (eaters of bacteria)Frederick Twort & Felix d’Herelle discovered viruses which infect bacteria.
1880 – Germ Theory
Robert Koch & Louis Pasteur
Pasteur identified rabies to be cause by an agent he termed “virus” from the Latin for ‘poison’.
100BC – China
Protection from smallpox using variolation practice
~1400BC
First written record of virus infections in heiroglyphics found in Memphis, Eygpt
Vaccination
Edward Jenner vaccinated a boy with cowpox-infected material
1892 beginning of virology
Dmitri Iwanowski showed that ceramic filtered extracts from diseased plants could transmit disease to other plants.
1909
Landsteiner & Popper
Poliomyelitis (Yellow Fever) was the first human disease to be recognized as a viral disease
Discoveries of Ebola, West Nile, HIV, SARS
Introduction – Structure – Replication – Virology – Medicine - Review

20. Techniques to Study Viruses
X-ray Crytallography – X-rays are directed at a sample. How those rays scatter can be used to determine the structure of that sample
Atomic Force Microscope – A tiny tip probes a surface, from which the shape of the surface can be determined

21. Sedimentary Centrifugation – A sample is spun so fast, different elements in it are separated by density
Filters – Very small holes in material filter only viruses through
Electron Microscope – Electrons are smaller than light wavelengths, so viruses can be “seen” by reflecting electrons off of them

22. Viruses Can Help Cells, Too
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
Introduction – Structure – Replication – Virology – Medicine - Review

23. Introduction – Structure – Replication – Virology – Medicine - Review
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

24. Introduction – Structure – Replication – Virology – Medicine - Review
The End
Introduction – Structure – Replication – Virology – Medicine - Review

25. VIRUS Organisms that live on or near a host and cause it harm.
Active Viruses
Hidden Viruses
Host
VIRUS
Parasite
Organisms that live on or near a host and cause it harm.
A living thing that provides a source of energy for a virus or an organism
A tiny, nonliving that invades and then multiplies inside of a cell.
Some viruses hide for a while and become part of the cell’s genetic material. It may stay inactive and “hidden” for years. Then under certain conditions it becomes active and acts like an active virus. Ex – cold sores
A virus that immediately goes into action. It begins to take over cell functions and produce the virus’s proteins and genetic material.These parts then assemble into new viruses. The viruses multiply like a copy machine left on. When it is full it bursts open – releases the new viruses and dies.

26. How Viruses Multiply Lysogenic
Active viruses enter cells and immediately begin to multiply, leading to the quick death of the invaded cells.

27. How Viruses Multiply Lytic
Hidden viruses “hide” for a while inside host cells before becoming active.