Onion Root Tip Mitosis Lab
- Students will be able to…
o Work in small groups to prepare an onion root tip squash and view it
under the microscope.
o Identify the phases of mitosis under the microscope
o Identify the stage of mitosis that requires the most time
o Apply knowledge of Mitosis by identifying mitosis stages in a teacher
prepared onion root tip slide.
Onions in water for 3 days
Forceps (aka Tweezers)
HCl (Hydrochloric Acid)
Carnoy (mixture of vinegar and alcohol)
Toluidine Blue (Blue dye)
Dropper for water
1. Use tweezers to transfer an onion root tip into a cup of HCl.
*This allows the cell wall to start to dissolve, so we can see inside the cell.
2. After 4 minutes, transfer the root into the Carnoy fluid for 4 minutes.
3. Place the root onto a slide.
4. Cover the root tip with one drop of Toluidine Blue (Blue dye) for 1 minute.
5. After 1 minute blot away the stain.
*Be extremely careful!!! Not to touch the root tip!! This will ruin your slide!!!
6. When the stain is blotted away carefully, cover the root tip with 1 to 2 drops of
*You may need to repeat this process several times until your blue dye is gone.
7. Gently lower a cover slip over the root tip.
8. Cover the slide with a paper towel and firmly press on the cover slip. Do not
twist the cover slip at all. This will press the root into a single cellular level. Use a
pencil tip to press down on top of the paper towel to make sure you have as thin as a
layer as possible.
9. Observe your preparation under the low power of a microscope.
10. Search your slide and try to find various stages of mitosis occurring!
Example of Cells in each stage of Cell Division.
Please include the following questions and drawings with your lab writeup.
1. When viewing your group slide under the microscope were you able to see
2. Were you able to see/identify various stages of mitosis? If so, which ones and
how many of each?
3. What is a distinguishing visible feature of each stage of mitosis?
Interphase Prophase Metaphase Anaphase Telophase Cytokinesis
# of cells # of cells # of cells # of cells # of cells # of cells
Drawings Drawings Drawings Drawings Drawings Drawings
Online Lab Results
Interphas Prophase Metaphase Anaphase Telophase Cytokinesi
e #_______ #________ #________ #________ s
#________ _ _ _ _ #_________
%________ %_______ %________ %________ %________ _
_ _ _ _ %_________
# of cells and quick sketch
1. Based on your data, how many cells were in each phase?
2. What phase had the most cells?
3. What phase had the least cells?
*Don’t forget to answer all usual questions on your lab packet as well as the
1. Why do you think that most of the cells were located in the phase that they
2. What happens in this phase that requires them to spend so much time there?
3. In comparing your own prepared slide with the online tutorial, did you have
similar results? If so, what do you think enabled you to receive these results?
If not, what do you think went wrong?
Carolina Biological Supply Company.
The Biology Project: The University of Arizona