Viruses

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Viruses
Non-Living Infectious Agents

• What are they?
• How do they work?
• Where do they come from?
• And What good are they?

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Non-viral Infectious Agents

• Viroids- The smallest known particle that can
  replicate.
• Single Strand of RNA
• Disrupt plant cell metabolism
• Can destroy entire crops
• Prions Abnormal forms of proteins that clump
  together inside cells.
• Clumping eventually
  kills the cell
• Example
• Mad Cow Disease

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Overview of Viruses

• Nonliving
• Composed of Nucleic acid and protein
• Cause many diseases
• Virology Study of Viruses
• Comparison of Viruses and Cells below

Char. Of Life Virus Cell
Growth No Yes
Homeostasis No Yes
Metabolism No Yes
Mutation Yes Yes
Nucleic acid DNA or RNA DNA
Reproduction Only within host cell Independently by cell division
Structure Nucleic acid core, protein covering, some have envelope Cytoplasm, cell membrane, etc..
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Characteristics of Viruses

• 2 essential features
• 1. Nucleic Acid
• May be DNA or RNA
• Helical, closed loop, or long strand
• 2. Protein Coat called CAPSID
• Some have ENVELOPE
• Ex. Influenza, chickenpox, herpes simplex, HIV
• VIRAL SHAPE
• Icosahedron 20 triangular faces
• Ex.) herpes, chickenpox, polio
• Helix Coiled spring
• EX.) Rabies, measles, tobacco mosaic

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• Bacteriophages like tiny little syringes that
  inject DNA from the virus into the cell

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Lytic Cycle
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Here is a non-enveloped bacteria virus inserting
its DNA into a bacterial cell.
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Some virus are pushed out by the cell, taking
some of the cell membrane with them.
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Lysogenic Cycle

• After Step 2 of the Lytic Cycle, the Virus may
  become Dormant and enter into the Lysogenic cycle
• Dormant- non-active time of virus
• Host is infected, but doesnt know it
• Ex Herpes (cold sores) Person doesnt have them
  all the time, but has outbreaks throughout year
• Ex HIV
• Mono

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Lysogenic Cycle
Provirus
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Classification of Viruses
1. By Shape 2. Host type 3.
function
Retroviruses attack a certain way. DNA viruses
attack another way.
Animal viruses
Plant viruses
Bacteria viruses
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Viruses and Human Disease

• Control and Prevention of spread.
• Vaccination Antiviral drugs
• Ex.) chickenpox vaccine, AZT, Acyclovir, protease
  inhibitors.
• Emerging Viruses exist in isolated habitats
• Do not usually infect humans unless environmental
  conditions favor contact.
• Several viruses are now linked to cancers such as
  leukemia, liver cancer, Burkitts lymphoma,
  cervical cancer.

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English physician and scientist from Berkeley,
Gloucestershire, who was the pioneer of smallpox
vaccine
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• Cowpox and smallpox are closely related, but
  cowpox is a much less serious disease than
  smallpox.
• Jenner noticed milkmaids were immune to smallpox.
• He used puss from a cowpox blister to inocculate
  an 8 year old boy
• He called his method vaccination, from the
  Latin word vacca, or cow, and today we use
  vaccination to refer to immunization against any
  disease.

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• A vaccine contains a killed/weakened part of a
  germ.
• When a person receives a vaccine, the body reacts
  by making protective antibodies.

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Wendell M. Stanley

• Wendell M. Stanley crystallized and described the
  molecular structure of the tobacco mosaic virus.

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PAPOVAVIRUSES Tumor causing virusesMost
common Human papillomavirus (HPV) (warts)
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ADENOVIRUSES causes respiratory issues and pink
eye
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HERPESVIRUSES easily transmitted by direct
contact with a lesion or the body fluid of an
infected individual
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POXVIRUSES
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PICORNAVIRUSESThe name is derived from pico,
meaning small, and RNA, referring to the
ribonucleic acid genome, so "pico-rna-virus"
literally means small RNA virus.Ranges from the
common cold to polio!
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MYXOVIRUSES
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RHABDOVIRUSES
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RETROVIRUSES genes are encoded in RNA instead
of DNA
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Here is a classic picture of HIV viral progeny
being released from the surface of a T- cell.
Notice the membrane coating they receive.
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Ebola Virus

• Some therapies that have worked have been when
  patients receive blood from convalescent patients

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