Binary Fission (AQA AS Biology): Revision Note

Binary fission of prokaryotic cells

• Cell division in prokaryotes is called binary fission

• It is simpler than mitosis as cells have no nucleus, chromosomes, spindle fibres, or membrane-bound organelles

• Prokaryotes only need to replicate

  • a single, circular DNA molecule

  • plasmids: small, circular DNA molecules

The process of binary fission

1. The circular DNA molecule is replicated

2. Plasmids replicate

3. The cytoplasm divides (roughly) equally between daughter cells

4. Each daughter cell is genetically identical and receives

   • one copy of circular DNA

   • 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, it dies