AQA A Level Biology复习笔记2.3.8 Binary Fission DOWNLOAD PDF

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

     

1.1.7-Binary-fission

The process of binary fission producing genetically identical daughter cells

 

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