Core Practical 5

• Where do plant cells undergo mitosis?

  At shoot and root tips in meristems
• What is the characteristic of cells in the meristems?

  They are totipotent and can differentiate
• What does the mitotic index represent?

  The ratio of cells undergoing mitosis
• How is the mitotic index calculated?

  By counting mitotic cells and total cells
• What equipment is needed to calculate the mitotic index?

  An optical microscope and garlic root tip
• What is the method for preparing a root tip sample for mitotic index calculation?

  1. Cut a 5mm sample of the root tip.
  2. Transfer to HCl for 5 minutes.
  3. Transfer to cold distilled water for 5 minutes.
  4. Dry on filter paper.
  5. Macerate on a microscope slide.
  6. Stain with toluidine blue for 2 minutes.
  7. Cover with a slip and avoid air bubbles.
  8. Squash the slide gently.
  9. Observe under a microscope.
• What is the purpose of using toluidine blue stain?

  To make chromosomes visible
• Why is it important to avoid air bubbles under the coverslip?

  They may distort the image
• What should be done if hydrochloric acid contacts the skin?

  Wash off skin immediately with water
• What safety precaution should be taken when using a scalpel?

  Cut away from fingers and use forceps
• What are the hazards and safety precautions associated with the experiment?

  Hazards:

  • Hydrochloric acid: Eye/skin irritation
  • Toluidine blue: Eye/skin irritation
  • Scalpel: Cuts from sharp object
  • Broken glass: Cuts from sharp object

  
  

  Safety Precautions:

  • Wear eye protection
  • Avoid skin contact
  • Cut away from fingers
  • Handle glassware carefully
• What should be done in case of a cut from a scalpel?

  Elevate cuts and apply pressure
• What is the risk level associated with using hydrochloric acid?

  Low
• What is the first step in the method for preparing the root tip sample?

  Cut a 5mm sample of the root tip
• What is the purpose of macerating the root tip?

  To spread the cells out for visibility
• What should be done after placing the root tip on the microscope slide?

  Macerate with a needle to spread cells
• How does the method ensure that chromosomes are visible during observation?

  By macerating the cells and staining
• What is the final step before observing the slide under the microscope?

  Use the fine adjustment knob to focus
• What is the role of the coarse adjustment knob in microscopy?

  To move the lens closer to the slide
• What should be done if the image is not clear under the microscope?

  Use the fine adjustment knob to re-focus
• What are totipotent cells?

  Cells that can differentiate into any cell type
• What is the definition of mitotic index?

  The ratio of mitotic cells to total cells
• Why is distilled water used in the method?

  To rinse the root tip after HCl treatment
• What is the significance of using a microscope slide and coverslip?

  To prepare the sample for observation
• What is the role of the optical microscope in this experiment?

  To observe the cells and their mitotic activity
• Why is it important to count cells with visible chromosomes?

  To determine the mitotic index accurately
• What is the procedure for using the fine adjustment knob?

  Carefully re-adjust focus until clear
• Why is it important to start with low magnification?

  To locate the cells before increasing magnification