Module 8: Genome

• what were the 3 genome revolutions?

  1. gene cloning
  2. PCR and DNA sequencing
  3. CRISPR
• genome: complete genetic content of cell or organism
• what is the size range of bacteria and archaea genomes?

  1.5-14 mb
• what are the contents of bacteria and archaea genomes?

  chromosomes and plasmids
• bacteria and archaea genomes are mostly coding seuqence
• what is the size range of eukarya genome?

  2-20,000 mb
• what are the contents of eukarya genome?

  chromosomes and organelles chromosomes (yeast also have plasmids)
• eukarya genome is mostly non-coding sequence
• chromosomes: essential genes
• what are examples of essential genes?

  ribosomes and DNA polymerase
• how many copies of a chromosome do bacteria have?

  haploid (1)
• bacteria chromosome shape and size: usually circular, 1-12 mb
• plasmids: encode accessory functions
• how do plasmids replicate?

  at origin of replication using host machinery
• how many copies of a plasmid are there?

  varies, 1-100s
• what is the shape and size of plasmids?

  usually circular dsDNA, 2-1000 kb
• what are examples of accessory functions?

  1. antibiotic production
  2. conjugation
  3. metabolic functions
  4. resistance
  5. virulence
• plasmid replication: independent, parasite to host cell
• plasmid-encoded proteins use cell's replication proteins
• plasmids can have a narrow or broad host range
• what is a plasmid with a broad host range?

  R-plasmids, any gram - bacteria
• plasmid segregation: ensure each daughter cell gets a plasmid
• how do plasmids with low copy numbers segregate?

  coordinate with chromosome replication, use host cytoskeleton to separate with cell
• how do plasmids with high copy numbers segregate?

  random partitioning into daughter cells
• toxin-antitoxin cells: toxin kills cell if plasmid is lost
• how does toxin-antitoxin system work?

  • antitoxin and toxin proteins in plasmid genome
  • antitoxin binds cellular toxin, is degraded without plasmid presence