All cells arise from other cells

• Mitosis

  Results in two genetically identical daughter cells
• Mitosis

  DNA replication occurs during the interphase stage of the cell
• Prophase

  1. Chromosomes become visible as long thin threads, which later shortens and thickens

  2. Spindle fibres develop from centrioles

  3. Nucleolus disappears and nuclear envelope breaks down - chromosomes are free in cytoplasm of cell

  4. Chromosomes drawn to equator of cell by spindle fibres
• Metaphase

  1. Chromosomes are seen to be made up of two chromatids joined by the centromere

  2. Chromosomes arrange themselves across middle of the cell
• Anaphase

  1. Centromeres divide into two, spindle fibres pull chromatids apart

  2. Chromatids move to opposite poles of the cell, now referred to as chromosomes

  3. Energy for the process provided by mitochondria

  4. If the cell is treated with chemicals that destroy the spindle, chromosomes remain at equator
• Telophase & Cytokinesis

  1. Chromosomes become longer and thinner after reaching opposite ends, before disappearing and leaving one widely spread chromatin

  2. Spindle fibres disintegrate, nucleolus and nuclear envelope reform

  3. Cytoplasm divides during cytokinesis
• Binary fission

  Cell division in prokaryotic cells
• Binary fission

  1. Circular DNA molecule replicates

  2. Both copies attach to cell membrane

  3. Plasmids also replicate

  4. Cell membrane grows between the two DNA molecules and begins to pinch inwards, dividing cytoplasm into two

  5. New cell wall forms between the two DNA molecules, forming two identical daughter cells
• Viral replication

  Viruses must replicate through living host cell
• Viral replication

  1. Viruses attach to host cell via attachment proteins on their surface

  2. They then inject nucleic acid into host cell

  3. Genetic information in nucleic acid provides instructions for host cell

  4. Host cell begins to produce the viral components needed for assembly of new viruses
• Cell cycle

  • Interphase: most of the cell cycle consists of interphase, no division takes place. "Resting phase"
  • Nuclear division: when the cell divides during either mitosis or meiosis
  • Cytokinesis: division of the cytoplasm to produce either two new cells or four new cells
• Cancer

  A group of diseases caused by a growth disorder of the cells. Result of damage to genes that regulate mitosis which lead to uncontrolled growth and division of cells
• Tumour

  • A group of abnormal cells that develop and constantly expand in size
  • Most commonly found in the lungs, breast, ovaries, stomach, pancreas
• Mutant cells

  • Different both structurally and functionally from other cells
  • Most mutated cells die -> surviving cells divide into clones and from tumours
• Malignant tumours


  • Grow rapidly, less compact. More likely to be life-threatening
• Benign tumours


  • Grow slowly, more compact. Less likely to be life-threatening
• Treatment of cancer

  1. Involves killing dividing cells by blocking part of cells

  2. Drugs used to treat cancer disrupt the cell cycle by: Preventing DNA from replicating, Inhibiting the metaphase stage of mitosis by interfering with spindle formation
• Issues with drug treatment

  Also disrupts cell cycle of normal cells. However, they are more effective against rapidly dividing cells