Mitosis root tip squash (P2)

• What is the aim of the root tip squash practical

  To observe the stages of mitosis and calculate the mitotic index in plant root tip cells
• why are root tips used in this practical

  because they contain actively dividing cells undergoing mitosis
• how is the mitotic index calculated

  mitotic index = (number of cells in mitosis / total number of cells) X 100
• what stains are used and why

  acetic orcein or toluidine blue to make chromosomes visible under a microscope
• What is the purpose of the mitosis root tip squash practical?

  To prepare a stained squash of cells
• What equipment is essential for the mitosis root tip squash practical?

  • Hydrochloric acid
  • Acetic orcein stain
  • Mounted needle
  • Scalpel
• Why is hydrochloric acid used in the practical?

  To soften the root tissues for squashing
• What color does acetic orcein stain the chromosomes?

  Dark reddy purple
• What is the function of the mounted needle in the experiment?

  To prevent air bubbles under the cover slip
• What part of the onion or garlic is used for the experiment?

  The last five millimeters of the root tip
• Why is the last five millimeters of the root tip important?

  It is the region where cells are dividing
• What temperature should the water bath be set to during the experiment?

  60 degrees Celsius
• What should be done after soaking the root tip in hydrochloric acid?

  Rinse the root tip in distilled water
• How should excess distilled water be removed from the slide?

  Using filter paper next to the slide
• Why is it important to add only two small drops of acetic orcein stain?

  To prevent overflow and ensure visibility
• What is the purpose of squashing the root tip?

  To create a thin layer for microscopy
• What should be avoided when squashing the root tip?

  Breaking the glass cover slip
• What is a hazard associated with using a scalpel?

  You could cut yourself
• How can you prevent cutting yourself with a scalpel?

  Cut away from yourself on a tile
• What is a risk associated with hydrochloric acid?

  It can be an irritant or corrosive
• What safety measure should be taken when using hydrochloric acid?

  Wear goggles to protect your eyes
• What should you do if hydrochloric acid gets on your hands?

  Wash your hands immediately
• What should you look for under the microscope during the experiment?

  Cells in various stages of mitosis
• What is the mitotic index?

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

  Cells in mitosis divided by total cells
• If there are 32 cells and 3 in mitosis, what is the mitotic index?

  $9.38\%$
• What should you do to ensure an accurate count of cells for the mitotic index?

  Examine multiple fields of view
• Why is it important to have a representative sample when counting cells?

  To ensure accurate mitotic index calculation
• What are the typical exam questions related to the mitosis root tip squash practical?

  1. Why use the first five millimeters of root tip?
  2. Why press down gently on the cover slip?
  3. Why use a stain in the experiment?
• What are the stages of mitosis that can be observed?

  • Anaphase: Chromatids pulled apart
  • Metaphase: Chromosomes align at the equator
  • Interphase: No visible chromosomes