bacterial genetics

• Genetics


  Science concerned with heredity and variation
• Bacteria


  • Haploid
• Modes of reproduction


  • Asexual
  • Sexual
• Asexual reproduction


  • Most common and important in bacterial growth cycle (e.g. fission)
  • No recombination
  • Changes arise through mutations
• Genetic recombination


  Exchange of genes between 2 DNA molecules to form combination of genes in a chromosome
• Sexual reproduction in bacteria

  • Not differentiated to somatic or gametic cells
  • 2 functional/mating types: Donor, Recipient
  • Unidirectional transfer of DNA
  • Gene transfer = genetic recombination = changes = variations
• Methods of gene transfer

  • Conjugation
  • Transduction
  • Transformation
• Plasmid


  Small ds circular DNA
• Episome


  Plasmid that exist with/out being integrated to host chromosome
• Conjugative plasmids


  Plasmids that have genes for the F factor
• F factor


  Fertility factor
• Transduction


  Mediated by phages
• Generalized transduction


  • A segment of DNA is carried from one bacterial cell to another by a bacterial virus called a bacteriophage or phage. The phage attaches to the bacterial cell and injects its nucleic acid into the host cell
• Specialized transduction


  • Involves the transfer of only few specific genes from one bacterial cell to another by means of a phage. The Lambda phage, which infects E coli, is a well-studied example of specialized transducing phage
• Transformation


  DNA transformation involves the transfer of naked DNA into a recipient cell. In the first step, double-stranded donor DNA binds to specific receptors on the surface of a competent cell