All cells arise from other cells

• What is the cell cycle?

  A limited number of cells in multicellular organisms retain the ability to divide and so replace themselves
• What is 'gap phase one'?

  At this phase, the cell grows and new cell structures and proteins are made.
• What is synthesis?


  Cell replicates its DNA, ready to divide by mitosis
• What is 'gap phase two'?

  At this phase, cells keep growing and proteins needed for cell division are made.
• What is the interphase of the cell cycle?

  Cell DNA is unravelled and replicated

  The organelles are replicated

  ATP content is increased
• Structure of a chromosome in

  mitosis

  Cells have 46 chromosomes/23 pairs

  
  

  during interphase identical copy of chromosomes is made a joined by a centromere
• Why do cells need to undergo mitosis?

  - Replace cells during tissue repair

  - Increase cell number during growth
• What are the 5 stages of mitosis?

  interphase, prophase, metaphase, anaphase, telophase
• What happens in prophase?

  a cell's genetic material condenses,

  
  

  centrioles start moving to opposite ends of the cell,

  
  

  a spindle starts to form, and the nuclear envelope breaks down
• What happens in metaphase?

  Chromosomes line up in the middle of the cell and become attached to the spindle by their centromere
• What happens in anaphase?

  Centromeres divide, separating sister chromatids

  spindles (proteins) contract pulling chromatids to opposite poles

  chromatids appear v-shaped
• Why is the many mitochondria at anaphase?

  The process is energy demanding

  
  

  from mitochondria where aerobic respiration takes place

  
  

  where it releases energy for spindle fibre to contract
• What happens in telophase?

  chromatids reach opposite poles

  chromatids uncoils

  nuclear envelope forms so two nuclei

  the cytoplasm divides (cytokinesis)

  there are two daughter cells that are genetically identical
• What is the mitotic index?

  The ratio between the number of cells in mitosis in a tissue and the total number of observed cells
• How to calculate mitotic index?

  number of cells in mitosis/total number of cells x 100
• In a stained sample of dividing cells, 29 cells were visible in one microscope field of view. Three of these cells had clearly visible chromosomes. What is the mitotic index of the view?

  MI = (3/29) x 100 = 10%
• What is mitosis?


  Controlled Cell division that generates new cells for growth and repair. The division of one cell into two genetically identical daughter cells
• What leads to cancer?

  uncontrolled cell division leading to the formation of tumours
• What are many cancer treatments directed at?

  controlling the rate of cell division
• What is a benign tumour?

  A growth of abnormal cells which is contained in one area within the body and will not invade other body parts
• What is a malignant tumour?

  A growth of abnormal cells which invade neighbouring tissues and spread to different parts of the body in the blood where they form secondary tumours. Malignant tumour cells are cancers
• What is chemotherapy?


  the use of drugs to destroy cancer cells
• Cancer treatments in Gap Phase 1 (Cell Growth & Protein production)

  - Chemical drugs used to prevent the synthesis of enzymes

  - which are needed for DNA Replication

  - the cell is unable to enter synthesis phase

  - disrupting the cell cycle

  - forcing the cell to kill itself
• Cancer treatments in S Phase (DNA replication)

  - Radiation & some drugs damage DNA

  - if severe DNA damages is detected

  - the cell kills itself (apoptosis)

  - preventing further tumour growth