Investigating mitosis

• What practical exercise is required by the AQA specifications?

  Investigating mitosis in root tip squashes
• What is the first step in the practical for investigating mitosis?

  Warm hydrochloric acid in a water bath
• What should be done after cutting the root tip?

  Wash the root tips in cold water
• Why is hydrochloric acid used in the practical?

  To separate plant cells for staining
• What does the stain bind to in the cells?

  Chromatin DNA
• How does using multiple root tips benefit the experiment?

  Increases chances of obtaining good images
• What can be observed using a light microscope in root tips?

  Different cells in stages of mitosis
• What is the mitotic index?

  Ratio of cells undergoing mitosis to total cells
• What does a high mitotic index indicate in fast-growing tissue?

  More cells are dividing
• What can a high mitotic index indicate in damaged tissue?

  Cells undergo mitosis to replace damage
• How is the mitotic index related to cancer?

  A high index can be a cancer marker
• What tool is used to measure actual cell size?

  Stage micrometer
• What is the purpose of calibrating the eyepiece graticule?

  To determine actual micrometer measurements
• What happens to the magnification of the eyepiece graticule?

  It does not change regardless of sample size
• How do you calculate the actual size of a cell?

  Using the formula with magnification
• What is the answer to the practice question regarding divisions?

  8 divisions
• What does one division of the stage micrometer equal?

  2.5 micrometers
• When should the eyepiece graticule be recalibrated?

  Whenever you change the magnification
• What are the steps for preparing root tip squashes for mitosis observation?

  1. Warm hydrochloric acid in a water bath.
  2. Cut 1-2 cm of root tip.
  3. Wash root tips in cold water.
  4. Transfer to warm acid for 5 minutes.
  5. Wash again and stain for 2 minutes.
  6. Spread cells on a slide and cover with a cover slip.
• What are the common questions related to the practical of investigating mitosis?

  • Why use multiple root tips?
  • Why is acid used?
  • What does the stain bind to?
  • How to improve end images?
• What are the implications of a high mitotic index?

  • Indicates rapid cell division in fast-growing tissues.
  • Can signal tissue repair in damaged areas.
  • May be a marker for cancer prognosis.
• What is the relationship between mitotic index and chemotherapy?

  • Higher mitotic index indicates worse prognosis.
  • Used to predict response to chemotherapy.
• What is the significance of using a stage micrometer in microscopy?

  • Provides accurate measurement of cell size.
  • Allows calibration of eyepiece graticule.