Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Bioterrorism wikipedia , lookup
West Nile fever wikipedia , lookup
Human cytomegalovirus wikipedia , lookup
Cross-species transmission wikipedia , lookup
Ebola virus disease wikipedia , lookup
Marburg virus disease wikipedia , lookup
Hepatitis B wikipedia , lookup
Orthohantavirus wikipedia , lookup
Henipavirus wikipedia , lookup
Influenza A virus wikipedia , lookup
VIRUSES NOTES Prior Knowledge • What are some viruses you are familiar with? • How do we cure virus infections? • Why do we have computer viruses? CHARACTERISTICS OF VIRUSES • Prokaryotic or Eukaryotic: Neither (no organelles or membranes) • Unicellular or Multicellular: Neither (nucleic acid covered by a protein) • Autotroph or Heterotroph: Neither (food is not metabolized for energy) • Which Kingdom do they belong to? None CHARACTERISTICS OF VIRUSES • 2 MAIN PARTS OF A VIRUS: 1. PROTEIN COAT (CAPSID): PROTECTS THE NUCLEIC ACID CORE 2. CORE OF NUCLEIC ACID (CAN BE DNA OR RNA) ▫ An envelope is found in some viruses (usually those that infect animal cells). It is an additional protective coating. EXAMPLE OF A BACTERIOPHAGE PROTEIN COAT (CAPSID) VIRAL DNA SHEATH TAIL FIBERS Viral morphology (shapes) (Label the diagrams) Typical Bacteria virus Animal virus Typical Plant virus Typical Viruses are sub-cellular • Viruses are among the smallest infectious agents • Most viruses cannot be seen by light microscopy and can only be seen by electron microscopy. • They are very small…20 to 300 nm. • They are so small that it would take 30,000 to 750,000 of them, side by side, to stretch to one cm. Proportional size of a virus to a bacteria HOW DO VIRUSES MULTIPLY? • Viruses perform replication in other cells called hosts. • The two replication cycles that viruses go through are the lytic and the lysogenic cycles. • The two cycles differ because in the lytic cycle a virus immediately replicates after entering the cell and in the lysogenic cycle the viral DNA replicates itself in a way that doesn’t kill the host cell immediately. • Bacteriophage = Virus that infects bacterial cells LYTIC CYCLE Quick Process Lytic cycle LYSOGENIC CYCLE Lysogenic Infection Slow Process prophage or provirus Lysogenic infection includes the lytic cycle as well. Lytic vs lysogenic • Viral infections that are lytic, destroy host cells quickly (& move on…) ▫ Ex: Ebola, Chicken Pox • Lysogenic infections destroy host cells slowly or not at all. Lysogenic viruses undergo lytic cycle when the host cell becomes stressed (may be recurring) ▫ Ex: HIV, herpes, Shingles HOW ARE VIRUSES CLASSIFIED? • VIRUSES CAN BE CLASSIFIED BY: ▫ A. SHAPE ▫ B. HOST ▫ C. FUNCTION Examples of Different Types of Human Viruses Influenza (Flu) Viruses leaving cell Examples of Different Types of Human Viruses Examples of Different Types of Human Viruses Smallpox & Hanta virus Examples of Different Types of Human Viruses Marburg & Lassa Examples of Different Types of Human Viruses Ebola THREE TYPES OF HOSTS A. PLANT Ex. Tobacco Mosaic Virus B. ANIMAL Ex. Rabies, Foot & Mouth Disease C. HUMAN Ex. Common cold, measles, chicken pox, mumps, HIV TREATMENT OF VIRAL DISEASES • Viral diseases cannot be cured by antibiotics. • Generally with viral infections you are limited to relieving symptoms while your immune system battles the virus. HUMAN USES FOR VIRUSES 1. VACCINES • When you inject a person with a harmless – weakened or dead form of a virus • This stimulates the immune system to produce cells and proteins that will destroy that type of virus, if it enters the body again • This helped to end epidemics of smallpox, polio and measles HUMAN USES FOR VIRUSES 2. GENETIC ENGINEERING • Viruses can help correct genetic defects by carrying desirable genes from one cell to another 3. AGRICULTURE • Help control pests that destroy human food crops • They eliminate harmful insects without creating pollution Viroids and Prions • Viroids have genetic material but no protein coat. • Prions are made of protein but have no nucleic acid. • Like viruses, viroids and prions are not made of cells but can cause disease. Viroids • Disease causing genetic material • Smallest known agents of infectious disease. • Made up of nucleic acid but uniquely characterized by the absence of a capsid. Prions • Disease causing proteins • A prion is a disease-causing agent • Unlike viruses they appear to lack nucleic acid (DNA or RNA). Mad-Cow Prion Diseased brain tissue caused by Mad-Cow Prion Infection • All viruses, viroids, and prions have a parasitic relationship with the host cell. • They require a host cell to replicate. Check for Understanding • What are the differences between viruses, viroids, and prions? Think about it…… •Is a virus alive? Viruses • Hard to classify as living, because: • Contain only a protein coat (capsid) and a nucleic acid core (DNA or RNA) ▫ May also contain a protein envelope that protects virus from host organism recognition • They don’t reproduce themselves… the virus is reproduced by the host cell