Cell Cycle

• Cell division


  The process by which a parent cell divides into two or more daughter cells
• Reasons for cell division

  • Reproduction
  • Growth
  • Repair
• Cell division for reproduction


  • Parent cells transfer genetic information to all offspring
  • Two types: asexual and sexual
• Asexual reproduction


  Producing offspring from any one parent, offspring are genetically identical to parent
• Sexual reproduction


  Producing offspring by the fusion of gametes, offspring have genetic material from both parents
• Cell division for growth

  • As organisms grow, the number of cells increases
  • Two important cellular processes: diffusion and osmosis
• Diffusion


  The movement of chemicals into and out of the cell from an area of higher concentration to an area of lower concentration
• Osmosis


  The movement of water from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration)
• Cell size is similar for the same type of cell
• As the amount of material in a cell increases, the speed of diffusion does not increase
• Smaller cells have a larger surface to volume ratio
• Cell division for repair

  • Cells divide to repair damaged cells
• Cell cycle


  The stages through which a cell passes as it grows and divides
• Stages of the cell cycle

  • Interphase
  • Mitosis
  • Cytokinesis
• The length of time to complete one cell cycle depends on the cell type
• Interphase


  • Longest stage of the cell cycle
  • 3 parts: G1 (cell growth), S (DNA replicates), G2 (cell growth and preparation for cell division)
• DNA within the nucleus during interphase consists of long, thin strands called chromatin
• Mitosis


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• Chromosomes consist of two identical sister chromatids held together by a centromere
• Spindle fibres (microtubules) attach to the centromeres and pull the sister chromatids to opposite poles of the cell
• Cytokinesis is the final stage of cell division, where the cytoplasm divides to form two genetically identical daughter cells
• Cell Cycle


  The series of events that a cell goes through as it grows and divides
• Stages of the Cell Cycle

  • Interphase
  • S (growth and DNA replication)
  • G₁ (growth)
  • G₂ (growth and final preparations for division)
  • M (mitosis)
  • Cytokinesis
• Mitosis (M phase)


  1. Prophase

  2. Metaphase

  3. Anaphase

  4. Telophase
• The stages of cell division are shorter than the cell cycle
• Cell division produces two daughter cells