Chapter 6

• Spike

  Protein appendage from the capsid or envelope that aids in the identification of the virus and the adherence of viruses to a host cell.
• Capsid


  Protein shell that protects the nucleic acid core, and aids in transfer between host cells.
• Envelope


  Facilitate binding to the host cell
• Nucleic acid


  Either DNA or RNA and is the genetic material of the virus.
• Matrix proteins/enzymes

  Lay between the capsid and the envelope.
• Virulent phages

  reproduce strictly through the lytic cycle
• Temperate phages

  phages that use both the lytic and lysogenic cycles
• Lytic cycle

  Enter cell, multiply, and lyse host cell.
• lysogenic cycle

  Integrate the viral genome into the host genome to become a phage.
• Lysogeny


  The condition that results from lysogenic conversion where the bacterial chromosomes contain phage DNA as well.
• Lysogenic conversion

  a bacterial cell receives new traits from the prophage.
• Provirus

  Viral DNA is incorporated into the host DNA of an animal and passed on to its progeny.
• Prophages

  A virus that is present in a bacterial cell but does not destroy the host cell.
• Animal viruses

  Go through a multiplication cycle through endocytosis and membrane fusion.
• Bacteriophage


  Go through the lytic or lysogenic cycle by injecting it's DNA into a bacterial cell.
• Characteristics that make viruses unique

  Replicate with a host cell, are non-living, have either DNA or RNA, lack cellular structure, smaller than cells and are acellular.
• Ways to classify viruses

  Structure, chemical composition and genetic makeup
• Animal Virus Replication

  adsorption, penetration, uncoating, synthesis, assembly, release
• Adsorption

  Capsid proteins or spikes attach to the surface of the host cell.
• Penetration

  Engulfed into the host cell
• Uncoated

  Freeing the RNA into the cytoplasm
• Synthesis

  Basic components of viruses are created such as RNA, casomers, and spikes.
• Assembly


  Viral spike proteins are inserted into the cell membrane and the envelope and capsid are forming from RNA and capsomers.
• Release

  Enveloped viruses leave the cell carrying an envelope with spikes and is ready to infect a new host cell.
• Host range

  Determine what species a virus can infect.
• Tissue tropism

  Determine what tissues or cells within a host will be infected by the virus.
• Characteristics that make virus genomes unique

  Have a smaller genome and only contain RNA or DNA
• naked virus penetration

  Enter the host cell through endocytosis by being engulfed.
• Enveloped viruses penetration

  Enter the host animal cell through endocytosis or membrane fusion.
• Naked viruses release

  The cell lyses or ruptures.
• Enveloped viruses release

  Bud off of the membrane of the host cell and take the spikes that are embedded into the membrane as well as part of the membrane to form the envelope.
• latent viral infection

  The virus is not released usually just sits and does not cause symtoms. Examples are cold sores, leukemia and shingles.
• chronic viral infection

  The virus is continously released and will cause symptos if not treated. Examples are cervical cancer, HIV, liver cancer, persisent enterovirus infection, progressive encephalitis and subacute sclerosing panencephalitis.
• Ways viruses can cause cancer

  Enter the cell and change the genetic material, carry genes that cause cancer, viruses produce proteins that cause loss of regulation of growth, and oncoviruses can cause malignant viruses.
• Prion diseases

  Occur when prions enter a nerve tissue, cause normal proteins to turn into prions, prions will multiplu and form chains. This will cause build up, which will cause cell function to decrease and turn into spongiform encepalopathies. Have a long incubation time and are deadly
• Examples of prion diseases

  Creutzfeld-Jacob Disease, Bovine Spongiform Encephalopathy (Mad Cow Disease), Scrapie, chronic wasting disease
• Difference in incubation of bacteria vs. viruses

  Viruses need a host cell in order to grow.
• Phage therapy

  When you give a person who has an bacterial infection a phage instead of antibiotics. The phage will directly target the bacteria that is making the person sick.
• Pros of phage therapy

  Can cause lysis to occur in infected host cells, target specific bacteria, FDA is looking into phages more, can treat MDR infections, phages can be modifyed and CRISPR can put phages directly into cells.
• Cons of phage therapy

  Scientists are unsure of effectiveness, idea is tied to the soviet union, case studies have not been performed, takes time to determine phage, not sure of adverse effects in the future, bacterial contents can go into the bloodstream after lysis.