backnext backnext contents 1. introduction 2. virus structure 3. virus replication 4. virology 5....
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CONTENTS
1. Introduction
2. Virus Structure
3. Virus Replication
4. Virology
5. Virus and Medicine
6. Review
Introduction – Structure – Replication – Virology – Medicine - Review
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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
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WHAT IS A VIRUS?
Introduction – Structure – Replication – Virology – Medicine – Review
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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
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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
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DISEASE VIRUSES
AIDS HIV
WartHerpes Simplex Virus
Flu Influenza
Measles Morbillivirus .
Cancer Hepatitis B
Introduction – Structure – Replication – Virology – Medicine - Review
Examples of some viral diseases:
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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
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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
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Cell BiologyLet'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
membranecytoplasm
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.
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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.
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How small is a virus?
Introduction – Structure – Replication – Virology – Medicine - Review
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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 m10-6 m
10-7 m
10-8 m
10-9 m
10-10 m
0 m
virusesanimalcellsbacteriap
rote
ins
ato
m
Go five more feet!
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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
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Tobacco Mosaic VirusTobacco 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
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Adenovirus
Introduction – Structure – Replication – Virology – Medicine - Review
Adenoviruses cause diseases like pink-eye or the common cold
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Bacteriophage
Introduction – Structure – Replication – Virology – Medicine - Review
Bacteriophage is a virus that infects bacteria.
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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.
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How do viruses replicate?
Introduction – Structure – Replication – Virology – Medicine - Review
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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 V
Phase 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
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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
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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
Metabolizes Doesn’t metabolize
Grows Doesn’t grow
Reproduces Reproduces
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A Brief History of Virology
Introduction – Structure – Replication – Virology – Medicine - Review
~1400BCFirst written record of virus infections in heiroglyphics found in Memphis, Eygpt
100BC – ChinaProtection from smallpox using variolation practice
1796 - Vaccination
Edward Jenner vaccinated a boy with cowpox-infected material
1880 – Germ TheoryRobert Koch & Louis Pasteur
Pasteur identified rabies to be cause by an agent he termed “virus” from the Latin for ‘poison’.
1892 beginning of
virologyDmitri Iwanowski showed that ceramic filtered extracts from diseased plants could transmit disease to other plants.
1898Martinus Beijerinick work on TMV
Freidrich Loeffler & Paul Frosch work on foot-and-mouth disease in cattle
1909Landsteiner & Popper
Poliomyelitis (Yellow Fever) was the first human disease to be recognized as a viral disease
1950-2003Discoveries of Ebola, West Nile, HIV, SARS
1915-1917Bacteriophages (eaters of bacteria)Frederick Twort & Felix d’Herelle discovered viruses which infect bacteria.
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Atomic Force Microscope – A tiny tip probes a surface, from which the shape of the surface can be determined
X-ray Crytallography – X-rays are directed at a sample. How those rays scatter can be used to determine the structure of that sample
Techniques to Study Viruses
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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
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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
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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
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The End
Introduction – Structure – Replication – Virology – Medicine - Review
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VIRUSA living thing that provides a source of energy for a virus or an organism
Organisms that live on or near a host and cause it harm.
A tiny, nonliving that invades and then multiplies inside of a cell.
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
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How Viruses Multiply•Active viruses enter cells and immediately begin to multiply, leading to the quick death of the invaded cells.
- Viruses
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How Viruses Multiply
•Hidden viruses “hide” for a while inside host cells before becoming active.
- Viruses
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Active and Hidden Viruses Activity
•Click the Active Art button to open a browser window and access Active Art
about active and hidden viruses.
- Viruses
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Deadly Virus
•Click the Video button to watch a movieabout deadly viruses.
- Viruses
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Common Viral Diseases
•Unlike with bacterial diseases, there are currently no medications that can cure viral infections.
- Viruses, Bacteria, and Your Health