Explains binary fission in bacteria, the simple division used by lower prokaryotes, step by step from DNA replication to splitting of the daughter cells. Then covers mitosis in eukaryotes: its four stages (prophase, metaphase, anaphase, telophase), how cytokinesis follows, and why errors can lead to apoptosis or cancer. The note closes with cell cycle control, describing cyclins and CDKs, the cyclin-CDK actions at each phase, tumour-suppressor inhibitor families (Cip/Kip and INK4a/ARF), and maturation-promoting factor.
Topic 27 of 63 in the MU Pleven syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 4 sections, about 809 words (6 min of reading), with 156 flashcards.
In this note
Cell reproduction. Mitosis.
Amitosis and Binary Fission
Mitosis
Control and Regulation of the Cell Cycle
Amitosis and Binary Fission
Amitosis, also called binary fission or direct division, is the type of cell division used by lower prokaryotes. It serves both for multiplication of cells and reproduction.
During bacterial cell division:
The circular DNA molecule, attached to the mesosome membrane, begins replication at the initiating point, located near the mesosome.
Chemical components of the mesosome trigger DNA replication, which is completed soon after initiation.
The replicated DNA molecules then attach to the membrane again, unfold, and segregate through a complex process.
In the middle region of the cell, the plasma membrane forms an inward invagination, which grows until the membranes fuse at the center, dividing the cytoplasm into two compartments.
Cell wall materials, such as peptidoglycans, are secreted between the newly formed plasma membranes.
Finally, the middle wall splits, separating the two daughter cells.
This process involves at least 20 or more genes and is highly regulated, demonstrating that even "simple" prokaryotic division is complex.
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