CPAC 6 A level Biology

• Where do plant cells undergo mitosis?

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

  They are totipotent and retain the ability to differentiate
• What does the mitotic index represent?

  The ratio of cells undergoing mitosis to the total number of cells in a sample
• How is the mitotic index calculated?

  By counting cells undergoing mitosis and the total number of cells
• What equipment is needed to calculate the mitotic index in plant cells?

  Garlic root tip, hydrochloric acid, toluidine blue stain, distilled water, and an optical microscope
• What is the method for preparing a root tip sample for mitotic index calculation?

  1. Cut a 5mm sample of the root tip using a scalpel.
  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 coverslip and remove air bubbles.
  8. Squash the slide gently.
  9. Observe under a microscope and adjust focus.
• What is the purpose of using toluidine blue stain in the procedure?

  To stain the cells and make the chromosomes visible
• Why is it important to avoid air bubbles when placing the coverslip on the slide?

  Air bubbles may distort the image
• What should be done if hydrochloric acid comes into contact with skin?

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

  Cut away from fingers and use forceps to hold the sample
• What are the hazards and safety precautions associated with the use of hydrochloric acid and toluidine blue stain?

  Hazards:

  • May cause harm/irritation to eyes or skin

  
  

  Safety Precautions:

  • Wear eye protection
  • Avoid contact with skin
  • Wash off immediately if contact occurs
• What should be done in case of cuts from a scalpel?

  Elevate cuts, apply pressure, and seek medical assistance
• What is the risk associated with broken glass during the experiment?

  It can cause cuts from sharp objects
• What should be done if a cut occurs from broken glass?

  Elevate the cut, apply pressure, and seek medical assistance
• What are the risks associated with the use of hydrochloric acid, toluidine blue stain, scalpel, and broken glass in the experiment?

  • Hydrochloric acid: Harm/irritation to eyes or skin
  • Toluidine blue: Harm/irritation to eyes or skin
  • Scalpel: Cuts from sharp object
  • Broken glass: Cuts from sharp object