A gallery of falsely coloured transmission electron micrograph images captures the presumed order of events when the HIV virus buds from the surface of a T-lymphocyte white blood cell. The virus particles attack T-lymphocytes, stealing their genetic machinery, thereby forcing them to produce more copies of the virus. (National Geographic.com) VIRUSES

Definition of Virus  A _____________ particle made up of protein- covered ________________that can invade living cells  The word comes from the Latin word ______ meaning a ___________________of plant or animal origin

Picture of a Virus  Spreading potentially lethal pathogens, ______________ particles (brown) invade cilia (blue) in the airways of the human lung.  Image by Karsten Schneider/Science Photo Library

Different Viruses:  The ____________ of a virus gives it a characteristic shape  All viruses have 2 parts: ________________an d a protein covering called a ________

Just How Big IS a Virus??

Classifying Viruses  Difficult to classify because viruses are ____ ________  They do NOT metabolize energy or perform ____________________  They must live as ___________ within the cells of a host organism  They depend on their hosts for respiration, nutrition and all other functions of life to enable them to reproduce

Classifying Viruses  Viruses ‘____________’ the host cell by altering its genetic make up  Viruses have characteristic shapes but all have 2 components: ______________(DNA or RNA) and a protein covering called a _______  Viruses...  Example: Plant viruses infect plants and animal viruses infect animal

Bacteriophage  ________ are viruses that only infect __________  They are also known as ________________

The Reproduction Cycle of Viruses  Are 2 ways a virus can ___________, depending on the type of virus  The ________ Cycle OR The _________ Cycle

Lytic Cycle Step 1: Virus _________ to the host cell wall (ex. E. Coli) by its _____

Lytic Cycle Step 2: Virus tail releases an __________ dissolving the cell wall which creates an opening in the cell

Lytic Cycle Step 3: The viral ______ then takes over the host cell and destroys the host _______.

Lytic Cycle Step 4: Viral DNA then instructs the cell to ________________ of the viral DNA and capsid

Lytic Cycle Step 5: The new viral components are assembled into 100 or so _______ of the original invader.

Lytic Cycle Step 6: Viruses produce lytic enzyme that causes the host cell to ______ (to burst open)

Lytic Cycle Step 7: When the host cell breaks apart, new viruses are __________ to infect other cells

Just So You Know....  Bacteria are not defenceless against _______________  Some bacteria have enzymes called _______ __________ that recognize foreign DNA  These restriction enzymes act like scissors and ‘___________’ the phage’s DNA making it useless!

Lysogenic Cycle Step 1: Virus enters a host but doesn’t take over by destroying its DNA. Instead, it _______ with the host DNA. (lysogeny)

Lysogenic Cycle Step 2: Cell _________ many times with the newly configured (combined) DNA

Lysogenic Cycle Step 3: Virus can be copied through many generations and lies ________

Lysogenic Cycle Step 4: The virus is _________ by some environmental stimulus.

Lysogenic Cycle Step 5: Once ________, the viral DNA instructs the host cell to manufacture new viruses using the ____ __________

Types of Viruses RNA VIRUSES  Have RNA instead of DNA as their genetic material  RNA never becomes part of the host DNA  RNA acts like messenger RNA in the cell  mRNA gets instructions to manufacture viruses and bypass host cell DNA  They are ______ viruses  Example: most ______ viruses such as Tobacco Mosaic Virus

Tobacco Mosaic Virus

Types of Viruses Retroviruses  Also contain RNA as genetic material vs. DNA  When a virus infects a cell, it makes a copy of _____________ from the viral RNA code  Remember, _________ genetic transfer is from DNA to RNA but these viruses ________ the direction of genetic information transfer from normal to ‘_____________’  i.e. – RNA to DNA (viral RNA copied to make the host viral DNA)  This reverse of direction gives rise to their name ______________

Type of Viruses Retroviruses Continued...  They are ____________ because there is no bursting of the cell  Example: ______ (human immunodeficiency virus) which can cause AIDS (acquired immunodeficiency syndrome)  The virus enters a human white blood cell and makes the cell make DNA from the viral RNA – the new DNA becomes part of the hereditary apparatus of the infected human cell  The host cell does not burst BUT changes in ________, ____________, and ________

HIV Structure of HIV Purple (artificially dyed) virions on surface of a salmon –coloured T cell.

Types of Viruses Viral Diseases  Viruses don't always use the lytic or lysogenic cycle  They sometimes leave the host cell by pushing through the _____________________  This causes them to become __________ by the host cell’s membrane  Now the disguised ‘_____________’ virus spreads through the body undetected  Example: influenza, chicken pox/shingles, measles, mumps, hepatitis (A, B,C), warts, distemper, yellow fever, mononucleosis, encephalitis and rabies

Chicken Pox Virus  Called __________ _______ virus (VZV)  Transmitted in airborne _________ exhaled from an infected person, the virus causes a low fever and a _____ of fluid-filled blisters

Encephalitis  Encephalitis, or inflammation of the brain tissue, is _______  When it strikes, it can be very serious, causing _________________________, _____________, ___________, and other symptoms depending on the part of the brain affected.  It is usually caused by one of several ________ infections, so it's sometimes referred to as viral encephalitis.  Viral encephalitis may develop during or after infection with any of several viral illnesses including influenza, herpes simplex, measles, mumps, rubella, rabies, chickenpox and arbovirus infection including west nile virus.

Virus Causes Coral Reef Bleaching?  A virus that kills _______ on coral reefs may be causing widespread _________, according to scientists at Plymouth Marine Laboratory (PML)  This bleaching is now reported in over ____ countries, across three major ________ and shows that viruses play an important role in _______________ dynamics.

Virus Causes Coral Reef Bleaching?  Mass bleaching events in 1998 and 2002 led to destruction of up to ______ of corals in some areas of the Great Barrier Reef and Indian Ocean and _______________ is widely believed to be responsible for the increased ___________ and ___________ of bleaching.  Until this discovery, the underlying cause and the mechanisms involved were largely unknown.

Virus Causes Coral Reef Bleaching?  Shown that the symbiotic algae contain a latent virus - it is only when they are stressed by _____________ or ____________ that the virus multiplies  Taken from: x?theme=textonly x?theme=textonly  This is still a ________ at this point