Investigating mitosis

• What is the main focus of the study material?

  Investigating mitosis
• Why is it necessary to add a stain when preparing a squash slide?

  To enhance visibility of chromosomes
• What is one suitable stain for observing mitosis?

  Acetic orcein
• How should a student squash the tissue on the slide?

  Gently press to avoid damaging chromosomes
• How does the mitotic index of root tip cells compare to mature leaf cells?

  Root tip cells have a higher mitotic index
• How do you calculate the mitotic index?

  Divide visible chromosomes by total cells
• If 30 cells are observed and 4 have visible chromosomes, what is the mitotic index?

  0.13
• How do you express the mitotic index as a percentage?

  Multiply by 100
• What is the actual size of a cell if it measures 5 mm at × 100 magnification?


  0.05 mm
• What is an eyepiece graticule?

  A transparent ruler with no units
• What is the purpose of a stage micrometer?

  To provide an accurate scale for measurement
• How do you calculate the size of one division on the eyepiece graticule?

  Divide stage micrometer length by eyepiece divisions
• If 1 division on the stage micrometer is 0.1 mm and equals 4.5 divisions on the eyepiece graticule, what is the size of 1 division on the eyepiece graticule?

  0.022 mm
• If a specimen is 14 eyepiece divisions long and each division is 0.022 mm, what is the specimen's length?

  0.308 mm
• What does an abnormally high mitotic index suggest?

  Possible uncontrolled cell division
• If a cell appears 9.0 mm across at × 200 magnification, what is its actual size?

  0.045 mm
• What are the steps to focus an optical microscope on a specimen?

  • Start with the lowest magnification
  • Place the slide on the stage
  • Use coarse focus to bring the stage up
  • Adjust fine focus for clarity
  • Center the specimen in the field of view
• What are the key components used to measure cell size under a microscope?

  • Eyepiece graticule
  • Stage micrometer
• What should you be prepared to answer in exams regarding practicals?

  • Questions on apparatus used
  • Techniques applied during experiments