AQA AS Biology

Revision Notes

2.3.8 Binary Fission

Binary Fission of Prokaryotic Cells

  • 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

Binary fission, downloadable IGCSE & GCSE Biology revision notesThe process of binary fission producing genetically identical daughter cells.

Exam Tip

The daughter cells produced by binary fission can have a different number of plasmid copies but they are still genetically identical! This is because they still contain the same genetic code (DNA base sequences) they just have more or less identical copies of that code.

Author:

Alistair graduated from Oxford University in 2014 with a degree in Biological Sciences. He has taught GCSE/IGCSE Biology, as well as Biology and Environmental Systems & Societies for the International Baccalaureate Diploma Programme. While teaching in Oxford, Alistair completed his MA Education as Head of Department for Environmental Systems and Societies.
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