2 - MITOSIS

• AIM?

  stained squashes of cells from plant root tips, set up and use of an optical microscope to identify stages of mitosis and calculate mitotic index
• WHY ARE THE TIPS OF SHOOTS AND ROOTS USED?

  contains meristems which have totipotent cells that are dividing/ differentiating and can retain this ability
• WHY IS HOT ACID USED?

  damages cell membrane and makes it permeable to allow stain to bind to DNA
• WHAT STAIN IS USED AND WHY?

  toluidine blue as it stains DNA
• WHAT SHOULD YOU DO WITH THE COVERSLIP AND WHY?

  lower carefully/ at an angle to prevent air bubbles
• HOW TO SET UP MICROSCOPE?

  • start on lowest magnification
  • focus using coarse then fine knob
  • then increase magnification
• RISK ASSESSMENT?

  hot acid and toluidine blue are irritants therefore goggles should be worn and skin must be washed if come into contact
• HOW TO CALCULATE MITOTIC INDEX?

  number of cells with visible chromosomes / total number of cells in sample
• KEY THINGS TO ENSURE WHEN CALCULATING MITOSIS?

  only include whole cells, value should be between 0 and 1
• HOW IS CANCER TREATED?

  prevent DNA replicating and inhibit metaphase by interfering with spindle fibre formation
• WHAT HAPPENS TO THE NUCLEAR ENVELOPE IN MITOSIS AND WHICH STAGES?

  prophase: nuclear envelope disintegrates

  telophase: nuclear envelope reforms