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

Transcription

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

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

5 A VIRUS is either DNA or RNA, that is protected by a protein coat called a CAPSID. DNA CAPSID VIRUS

6 Why are some viruses harmful? Virus invades cell Virus forces cell to make copies of virus When your cells make viruses instead of operating normally, YOU get sick Eventually so many copies are made, the cell explodes, releasing all of the new viruses

7 Examples of some viral diseases: DISEASE AIDS Wart Flu VIRUSES HIV Herpes Simplex Virus Influenza Measles Morbillivirus. Cancer Hepatitis B

8 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

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.

10 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: Nucleus this holds the DNA or genetic information about the cell. Cytoplasm this is the factory where biochemical reactions occur. nucleus Membrane this double layer protects the cell and allows the cell to communicate with the outside environment. cytoplasm membrane

11 DNA/RNA DNA or RNA code for genes that defines who we are. 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.

12 How small is a virus?

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

14 Helical Capsids RNA Helical capsids are rodlike structures with the RNA in the center of the helix. A helix is made by stacking repeating units in a spiral. protein coat

15 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

16 Adenovirus Adenoviruses cause diseases like pink-eye or the common cold

17 Bacteriophage Bacteriophage is a virus that infects bacteria.

18 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.

19 How do viruses replicate?

20 Replication Phases 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 V - Release - Assembly of virus DNA and protein coat into whole new viruses - Leaving the cell Phase II Phase III Phase I Phase IV Phase V

21 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.

22 Are Viruses Living? Create a table where one column represent properties of living organisms and the second column represent properties of a virus. Properties of Living Organisms Breathes (respires) Metabolizes Grows Reproduces Properties of Viruses Doesn t breathe Doesn t metabolize Doesn t grow Reproduces

23 A Brief History of Virology 100BC China Protection from smallpox using variolation practice 1880 Germ Theory Robert Koch & Louis Pasteur Pasteur identified rabies to be cause by an agent he termed virus from the Latin for poison 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. ~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 Landsteiner & Popper Poliomyelitis (Yellow Fever) was the first human disease to be recognized as a viral disease Discoveries of Ebola, West Nile, HIV, SARS

24 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

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

26 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

27 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.

28 The End

29 A living thing that provides a source of energy for a virus or an organism VIRUS A tiny, nonliving that invades and then multiplies inside of a cell. Organisms that live on or near a host and cause it harm. 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. 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

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

31 - Viruses How Viruses Multiply Hidden viruses hide for a while inside host cells before becoming active.

32 - Viruses Active and Hidden Viruses Activity Click the Active Art button to open a browser window and access Active Art about active and hidden viruses.

33 - Viruses Deadly Virus Click the Video button to watch a movie about deadly viruses.

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