cell division & the cell cycle

• Cell Division


  A series of stages called the cell cycle
• Cell Division


  • Used by multicellular organisms to grow and repair damaged tissues
  • Used by some organisms for asexual reproduction
• Chromosomes


  • Structures in the nucleus of a cell made of DNA molecules
  • Sections called genes control the manufacture of particular proteins
• In body cells, the chromosomes exist in pairs. For instance, in humans, there are 23 pairs
• Mitosis and the Cell Cycle


  1. DNA replicates to form two copies of each chromosome

  2. Copies form an X shape

  3. Cell grows and increases the number of subcellular structures

  4. Any damaged DNA is also repaired

  5. Nucleus breaks down and spindle fibres form

  6. Chromosomes line up at the centre and attach to spindle fibres

  7. Replicated chromosomes separate and move to opposite ends

  8. Membranes develop around each set of chromosomes to form the nuclei of the two new cells

  9. Cytoplasm and membrane of the parent cell divide, forming two identical daughter cells
• Stem Cells


  Undifferentiated cells that can develop into different cell types
• There are parallel pathways for individual stem cells to develop into different cell types