Viruses

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VIRUSES : 

VIRUSES Diversity of Life 1 M.Bregar (Dante C.S.S.)

Not these kinds of viruses….. : 

Not these kinds of viruses….. 2 M.Bregar (Dante C.S.S.)

Viruses : 

Viruses Viruses are microscopic particles which Do not replicate or reproduce Do not grow/mature Are parasitic, only reproducing within a living orgnanism 3 M.Bregar (Dante C.S.S.)

Viral History : 

Viral History Beijerinck (1897) coined the Latin name “virus” meaning poison He studied filtered plant juices & found they caused healthy plants to become sick 4 M.Bregar (Dante C.S.S.)

Viral History : 

Viral History Small Pox Edward Jenner (1796) developed a smallpox vaccine using milder cowpox viruses Deadly viruses are said to be virulent Smallpox has been eradicated in the world today 5 M.Bregar (Dante C.S.S.)

Viral History : 

Viral History Tobacco Mosaic Virus Wendell Stanley (1935) studies crystallized sap from sick tobacco plants He discovered viruses were made of nucleic acid and protein 6 M.Bregar (Dante C.S.S.)

Where do Viruses Come From? : 

Where do Viruses Come From? Where do viruses come from? Problems in answering this question are: Viruses are very small, so no fossil record Only discovered about 100 years ago, we don’t know much about them 7 M.Bregar (Dante C.S.S.)

Where do Viruses Come From? : 

Where do Viruses Come From? They’ve been around for at least 4000 yeas. Small Pox First virus in recorded history Pharoah Ramses V (1196 B.C.) had the pot marks associated with small pox 3 Theories on viruses: 8 M.Bregar (Dante C.S.S.)

Slide 9: 

9 M.Bregar (Dante C.S.S.)

(1) Evolved from Cells : 

(1) Evolved from Cells Some cells evolved into viruses: By losing their genetic material, thus requiring the genetic material of host cells When fragments of a cell’s DNA combined to make something new (a virus) 10 M.Bregar (Dante C.S.S.)

(2) Evolved with Cells : 

(2) Evolved with Cells Simple molecules on earth evolved into: Cells which have self-replicating abilities or Viruses which have parasitic abilities, using cells to reproduce 11 M.Bregar (Dante C.S.S.)

(3) Alien Theory : 

(3) Alien Theory Idea that viruses came to Earth via a meteor Why such a strange idea? Viruses are so different from everything else on Earth 12 M.Bregar (Dante C.S.S.)

Characteristics of Viruses : 

Characteristics of Viruses 13 M.Bregar (Dante C.S.S.)

Characteristics of Viruses : 

Characteristics of Viruses Outside a living cell, viruses are lifeless Once inside a LIVING cell, viruses become alive to reproduce Debate …are viruses alive or non-alive? 14 M.Bregar (Dante C.S.S.)

Characteristics of Living Things : 

Characteristics of Living Things The following are characteristics of living things Maintain homeostasis – a steady internal state Have the ability to reproduce Have some sort of cellular organization / function Have metabolism – use chemical energy to survive Contain genetic information 15 M.Bregar (Dante C.S.S.)

Are Viruses Alive? : 

Are Viruses Alive? Viruses are non-living because: Do not grow Do not reproduce Do not me Viruses SEEM living because: They evolve/adapt Mutate 16 M.Bregar (Dante C.S.S.)

Viruses are Parasitic : 

Viruses are Parasitic All viruses are parasitic, meaning that they require another organism for their continued survival Generally: Outside of host cells, viruses are inactive Lack ribosomes and enzymes needed for metabolism Use the raw materials and enzymes of the host cell to be able to reproduce 17 M.Bregar (Dante C.S.S.)

Viral Structure : 

Viral Structure 18 M.Bregar (Dante C.S.S.)

Virus Structure : 

Virus Structure Viruses are simple structures consisting of Capsid A protein coat made of individual protein subunits called capsomeres Provides the virus with its shape Makes up 95% of a virus’s size Genetic Material Genetic material is located inside the capsid Can be DNA or RNA 19 M.Bregar (Dante C.S.S.)

The Capsid : 

The Capsid CAPSOMERES 20 M.Bregar (Dante C.S.S.)

Virus Structure : 

Virus Structure Spikes Located on capsid Helps viruses attach to cells Not present on all viruses Envelope Above capsid A protective coat on some viruses CAPSID DNA SPIKES ENVELOPE 21 M.Bregar (Dante C.S.S.)

Virus Structure : 

Virus Structure 22 M.Bregar (Dante C.S.S.)

Virus Structure : 

Virus Structure 23 M.Bregar (Dante C.S.S.)

Virus Shape : 

Virus Shape Viruses come in an assortment of different shapes, but most are geometrical There are 3 basic classification for viral shapes: 24 M.Bregar (Dante C.S.S.)

(1) Helical Shape : 

(1) Helical Shape Like the Ebola virus 25 M.Bregar (Dante C.S.S.)

(2) Polyhedral Viruses : 

(2) Polyhedral Viruses Like the Influenza virus 26 M.Bregar (Dante C.S.S.)

(3) Complex Viruses : 

(3) Complex Viruses Like the Bacteriophage 27 M.Bregar (Dante C.S.S.)

Virus Shape : 

Virus Shape 28 M.Bregar (Dante C.S.S.)

Viruses are Small : 

Viruses are Small Viruses are small (measure in nanometers) Viruses not viewed until the invention of the electron microscope About 100 times smaller than a red blood cell 29 M.Bregar (Dante C.S.S.)

Viruses are Small : 

Viruses are Small 30 M.Bregar (Dante C.S.S.)

Viral Reproduction : 

Viral Reproduction 31 M.Bregar (Dante C.S.S.)

Viral Specificity : 

Viral Specificity Viruses are HOST SPECIFIC, meaning they are adapted to infect a specific species Example – all Eukaryotic viruses have protective envelopes Host Range: The limited number of species a virus can infect Most viruses have a narrow host range 32 M.Bregar (Dante C.S.S.)

Bacteriophages : 

Bacteriophages Known as “eaters of bacteria” Have a unique tadpole shape Attack bacteria, inject their own DNA into the bacteria Have provided us with most of our information about viral reproduction 33 M.Bregar (Dante C.S.S.)

Bacteriophages : 

Bacteriophages 34 M.Bregar (Dante C.S.S.)

Virus Life Cycle : 

Virus Life Cycle Has two major stages: Viron Stage (usually outside of the cell) Dormant and usually transmitted at this stage Its “bad news” (DNA) wrapped in a protein coat Not functioning Infectious Stage Active, typically inside the cell Performs its life process – Viral Replication 35 M.Bregar (Dante C.S.S.)

Viral Replication (lyctic cycle) : 

Viral Replication (lyctic cycle) Viral replication occurs in 4 steps: Attachment & Penetration: Virus attaches to host cell using tail fibers Injects its OWN genetic material by forcing its tail sheath through the membrane 36 M.Bregar (Dante C.S.S.)

Viral Replication (lyctic cycle) : 

Viral Replication (lyctic cycle) Biosynthesis Viral DNA takes over the cell The host cell begins producing viral protein and nucleic acids (DNA) 37 M.Bregar (Dante C.S.S.)

Viral Replication (lyctic cycle) : 

Viral Replication (lyctic cycle) Maturation / Assembly New viruses are assembled from the viral parts produced by the host cell 38 M.Bregar (Dante C.S.S.)

Viral Replication (lyctic cycle) : 

Viral Replication (lyctic cycle) Release Newly formed viruses are released from the host cell 39 M.Bregar (Dante C.S.S.)

Viral Replication : 

Viral Replication Entire process known as the lytic cycle may be completed in as little as 25 to 45 min and produced as many as 300 new virus particles A virus that causes lysis of the host cell is said to be a virulent phage 40 M.Bregar (Dante C.S.S.)

Viral Replication : 

Viral Replication 41 M.Bregar (Dante C.S.S.)

Lysogenic Cycle : 

Lysogenic Cycle Certain types of virus, especially cancer causing viruses, have a lysogenic cycle The virus does not kill the host cell outright The DNA or RNA from the virus is incorporated into the DNA of the host cell and carried through many generations without apparent harm to the host The virus appears to be in a dormant state called lysogeny (dormancy) 42 M.Bregar (Dante C.S.S.)

Viruses & Human Beings : 

Viruses & Human Beings 43 M.Bregar (Dante C.S.S.)

Viruses & Human Health : 

Viruses & Human Health Many serious diseases are caused by viruses Symptoms are caused by destruction of the cell the viruses infect Antibiotics are not effective against viruses Viral diseases can be prevented with vaccines The body reacts to the vaccine as though it were the real disease and produces antibodies 44 M.Bregar (Dante C.S.S.)

Vaccines : 

Vaccines This is a prepared virus that has been HEATED to kill/destroy the genetic material while leaving the capsid (protein coat) intact. Vaccine is injected into a host, to trigger the immune system Immune system builds antibodies specific to that virus 45 M.Bregar (Dante C.S.S.)

How are viruses transmitted? : 

How are viruses transmitted? 46 M.Bregar (Dante C.S.S.)

Airborne : 

Airborne 47 M.Bregar (Dante C.S.S.)

Contaminated food or water : 

Contaminated food or water 48 M.Bregar (Dante C.S.S.)

Sexual contact : 

Sexual contact 49 M.Bregar (Dante C.S.S.)

Vectors or infected animal bite : 

Vectors or infected animal bite 50 M.Bregar (Dante C.S.S.)

Contaminated blood products : 

Contaminated blood products 51 M.Bregar (Dante C.S.S.)

Some viruses…… : 

Some viruses…… Small Pox 52 M.Bregar (Dante C.S.S.)

Some viruses…… : 

Some viruses…… Polio 53 M.Bregar (Dante C.S.S.)

Some viruses…… : 

Some viruses…… Ebola 54 M.Bregar (Dante C.S.S.)

Some viruses…… : 

Some viruses…… HIV 55 M.Bregar (Dante C.S.S.)