Observations using optical microscope

• what can you use to observe cells?

  An optical microscope
• How do you use an optical microscope to observe the prepped root tip cells?

  1. Clip the slide you have prepared onto the stage
  2. Select the lowest-powered lens
  3. Use the coarse adjustment knob to bring the stage up to just below the objective lens
  4. Look down the eyepiece. use coarse adjustment knob to move the stage downwards, away from objective lens until the image is roughly in focus
  5. adjust focus with fine adjustment knob, until image is clear
• what should you do if you need to see the slide with greater magnification?

  swap to a higher-powered objective lens and refocus
• what is the mitotic index?

  The proportion of cells undergoing mitosis
• How do you calculate mitotic index?

  mitotic index = no of cells with visible chromosomes / total number of cells observed
• what does working out the mitotic index let you work out?

  • How quickly the tissue is growing
  • A plant root tip is constantly growing = expect high mitotic indexx
• what does a high mitotic index for a plant cell mean?

  lots of cells in mitosis
• in other tissue samples, what could a high mitotic index mean?

  that tissue repair is taking place OR there is cancerous growth in the tissue