Final Review Micro

• Genotype


  Potential traits of an organism (all genes) whether expressed or not
• Phenotype


  Observable traits expressed due to the environmental conditions the organism is grown in
• Mutations


  • Heritable changes in DNA base sequences that affect phenotypic traits
  • Genotypes can change through mutation or horizontal gene transfer
• Prototrophic


  Wild type, grows on minimal media
• Auxotrophic


  Can't produce an essential enzyme or other molecules, will only grow on media containing the "missing substance"
• Types of Mutations


  • Wild-type
  • Missense
  • Nonsense
  • Deletion/Insertion
• Spontaneous mutations


  Occasional mistakes in DNA replication, transposons, normal low level radiation, one in a million
• Induced mutations


  Mutagens: chemicals, radiation, carcinogens
• Genetic Transfer


  1. Physical exchange of DNA between donor and recipient cells making a recombinant cell

  2. Homologous genetic recombination needed for stable incorporation of new DNA pieces into replicon

  
• Conjugation


  DNA transfers between two living bacterial cells in physical contact, ex. sex pilus in gram negative

  
• F Plasmid of E. Coli


  • Encodes proteins including F pilus, brings cells into contact, enzyme cuts plasmid, single strand transferred, complementary strands synthesized, both cells are now F+

  
• Transformation


  Transfer of naked DNA from donor to competent recipient cell, recipient cell integrates foreign DNA into its genome

  
• Griffith's Rat Experiment
• Transduction


  Involves using certain types of bacterial viruses (bacteriophages)

  
• Restriction Endonuclease Enzymes


  Prokaryotic DNA-cutting enzymes that are able to bind and cut to specific nucleotide sequences
• Polymerase Chain Reaction (PCR)


  DNA replication done in vitro
• Virion


  Mature, infectious, totally assembled complete virus particle that can be transferred between host cells
• Nucleocapsid


  Viral nucleic acid encased by protein coat
• Capsid


  Protein coat, composed of subunits (capsomeres)
• Envelope


  Composed of lipid membrane derived from host's cellular/nuclear membrane
• Components of a Virus (Bacteriophage)


  • Contains either DNA or RNA (can be single or double stranded, can be positive or negative stranded, positive mRNA is used for protein synthesis)
  • Has a protein coat surrounding nucleic acid
  • May contain an additional layer of lipids around the protein in enveloped viruses

  
• Taxonomy


  Science that studies organisms in order to arrange them into groups
• 3 Major Concerns of Taxonomy


  • Identification
  • Classification
  • Nomenclature
• Phylogeny


  Refers to evolutionary relatedness
• Linnaeus' Scheme involves Binomial System of Nomenclature – Genus and Species
• Bergey's Manual is used as a resource for identifying prokaryotic organisms
• Types of Bacteriophages


  • Virulent (Lytic)
  • Temperate (Lysogenic)
• Virulent (Lytic) Bacteriophages


  Phage enters and exits host, cell is lysed, process takes ~ 30 mins
• Temperate (Lysogenic) Bacteriophages


  No production of new virions
• Bacteriophage Infection Steps


  1. Attachment

  2. Infection

  3. Synthesis of Phage

  4. Assembly

  5. Lysis
• Attachment


  Collision between virus and host bacterium, attach at host surface receptors
• Infection


  Virus nucleic acid injected into host, viral coat protein stays outside cell

  
• Synthesis of Phage


  Viral nucleic acid replicated early, Eclipse period = Virions not yet assembled

  
• Assembly


  Assembly of virions
• Lysis


  Viral lysozyme causes cell to lyse
• Cultivation of Viruses


  • Animals
  • Plants
  • Chicken Embryo
  • Tissue Culture
• Lysogenic Phase


  Viral genes can be expressed without virion production, environmental conditions cause damage to host cell which triggers the phage to exit host chromosome and enter lytic cycle

  
• Latent Viruses


  Some animal and human viruses can remain latent (not multiplying or causing disease), environment may trigger replication and disease
• Latent Viruses


  • herpes zoster virus, chicken pox and shingles
• Oncogenic Viruses


  Once inside host cell, alter growth and metabolism (cancerous transformation), host cell can have increased rate of growth, altered chromosomes, altered surface molecules, ability to divide indefinitely