Stages of Mitosis in Onion Root Cells

Introduction

Because some stages of the cell cycle occupy longer amounts of time than others, some stages of the cycle (including different phases of mitosis) will be more common than others within any micrograph of root tip cells.  Thus, the numbers of cells in each phase within a particular slide, will give a rough idea of how much time the cells spend in each phase.

Safety Precautions

• Be careful handling glass slides, as the edges may be sharp.
• Observe proper use of the microscope; avoid handling the electric cord with wet hands.
• Do not use the coarse adjustment knob of the microscope at higher magnifications.
• Inform your teacher immediately of any broken glassware, as it could cause injuries.

Materials

• Prepared microscope slides of stained onion root tips or online images and resources.

  

This video provides a demo of materials including onion or garlic bulbs, germination of root, preparation of root tip, staining and observing under the microscope:

For this activity, you will work in pairs.

Procedure

Step 1:  Project an image of onion tip cells on a whiteboard.   Consulting with your team, identify and mark all the cells you feel are in interphase, and mark them with a particular color of marker pen.  Repeat for prophase, metaphase, anaphase, and telophase cells, and cells in cytokinesis.

Step 2:  In your lab notebook, make a table in which you list the number of cells in each phase.  Have an additional column that lists the percentage of the total number of classified cells that each number comprises.  Write down the formula you used to calculate the percentages.

Discussion

Do you think that a cell from a part of the root other than the tip, would have more or fewer cells in the active steps of mitosis (all phases other than interphase)?  Explain why.