Binary Fission (AQA A Level Biology)

• The process of cell division (binary fission) in prokaryotic cells is much simpler than mitosis in eukaryotic cells
• Prokaryotic cells do not possess:
  • A nucleus
  • Chromosomes
  • Membrane-bound organelles
  • Spindle fibres

• They have a single, circular DNA molecule and plasmids
  • Plasmids are smaller, circular DNA molecules that are also replicated and inherited
  • The number of copies of plasmids that each cell inherits can vary, although this number is regulated

The process of binary fission

• Binary fission is substantially different from mitosis as there is no nuclear envelope to breakdown and there are no spindle fibres present
• The process:
  • The single, circular DNA molecule undergoes DNA replication
  • Any plasmids present undergo DNA replication
  • The parent cell divides into two cells, with the cytoplasm roughly halved between the two daughter cells
  • The two daughter cells each contain a single copy of the circular DNA molecule and a variable number of plasmids

• There are mechanisms to ensure that all daughter cells inherit a copy of the single, circular DNA molecule along with some plasmids
  • If a daughter cell does not receive the single circular DNA molecule or at least one copy of a plasmid they die

The process of binary fission producing genetically identical daughter cells