Virology

• Classification - Study of diversity of organisms and evolutionary relationships
• Classification consists of Taxonomy and Phylogeny
• Taxonomy- Naming, describing, classifying (binomical nomenclature)
• Phylogeny - Evolutionary history of species or group
• Linnaean Classification is hierarchical meaning each level is more inclusive than the one below
• Taxon - Grouping at any level
• Domain - Kingdom - Phylum - Class - Order - Family - Genus - Species - Subspecies
• Evolution - Changes in allele frequency form generation to generation
• Natural Selection is the mechanism of evolution; beneficial traits increase in frequency over generations, and it requires heritable phenotypic variation
• Phylogeny - evolutionary history of a species or group of species
• Phylogenetic Tree - Representation of evolutionary relationships, shows pattern of descent from common ancestors
• Tree of Life: Domains - Eukarya, Archaea, Bacteria
• Virus characteristics - Subcellular, intracellular, parasites, Capsis+Genome, usually smaller than cells, Replicate within cells, Uses cell's resources for own life cycle
• Viruses Do Not: Carry out metabolic processes, Reproduce independent of host cells, Contain nucleus, cytoplasm, organelles (they are not cells)
• Virus Genetic Material - DNA or RNA, single/double-stranded, Linear, circular, segmented, 2-1000+ gene
• Capsid - Protein coat, made of capsomeres, determines morphology, involved in attachment to host cell
• Capsomeres - Capsid proteins
• Envelopes - phospholipid bilayer surrounding capsid, only present in some viruses, acquired from host, contains host and virus proteins
• Host range - species or tissue that a particular virus can infect, often limited to specific tissue, specificity due to interaction with host
• Virus Replication Cycle:

  1. Bind to host cell
  2. Genome enters cell
  3. Genome replication and gene expression
  4. Assembly
  5. Exit
• Bacteriophages - viruses that eat/infects bacteria
• Lytic Cycle: Horizontal transmission, virulent phages
• Horizontal transmission - host to host
• Virulent phages - phages that can cause disease in a host organism
• Lysogenic Cycle:

  1. Replication of viral genome without destroying host cell
  2. Phage genome integrates in to bacterial chromosome
  3. When host replicates, phage genome replicates
  4. Vertical transmission
• Vertical transmission - parent to offspring
• Vertical Transmission Visual

  
• Temperate Phage - Capable of lytic and lysogenic replication
• Bacterial Defenses - Resistance to infection, Restriction enzymes
• Restriction enzymes - enzymes that cut DNA at specific sequences called recognition sites
• Lytic Cycle Visual

  
• Vertical Transmission Visual

  
• Phage theta Replication

  
• Resistance to Infection visual

  
• Restriction enzymes Visual