VIRUSES!

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

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

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

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

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

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

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

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

Viruses range in size from 20 nanometers (nm) – 250 nanometers (nm) 1 nm = 0.001 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

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

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

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

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

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

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

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 http://www.cat.cc.md.us/courses/bio141/lecguide/unit2/viruses/adlyt.html Introduction – Structure – Replication – Virology – Medicine - Review

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

A Brief History of Virology 1898 Martinus Beijerinick work on TMV Freidrich Loeffler & Paul Frosch work on foot-and-mouth disease in cattle 1915-1917 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 1796 - 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 1950-2003 Discoveries of Ebola, West Nile, HIV, SARS Introduction – Structure – Replication – Virology – Medicine - Review

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

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

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

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

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

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.

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

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