Mitosis in Onion Root‐Tip Cells LAB
Purpose: To observe the steps of Interphase, Mitosis & Cytokinesis in an Onion Cell. In this activity,
you will estimate the relative duration of each phase of mitosis in onion root tip cells. The assumption is
that the number of cells observed to be in a phase is related to the amount of time spent in that phase.
Background: Although it is really a continuous process, mitotic cell division is usually described in four
stages: prophase, metaphase, anaphase and telophase. A fifth stage, interphase, describes the non‐
dividing cell. You will observe mitosis in microscope pictures of onion root tip cells.
Materials: Microscope, prepared slide onion root tip or whitefish blastula, Mitosis Onion Root CARD
Procedure A
1. Using the microscope, observe a prepared slide of an onion cell Allium (onion root tip) under 400X
magnification.
2. Try to find these steps in each of the cell & then draw below.
a. Interphase
b. Prophase
c. Metaphase
d. Anaphase
e. Telophase
Procedure B
1. Count the number of cells that are in each stage of interphase & mitosis (prophase, metaphase,
anaphase and telophase) and record in the table.
2. Given that it takes on average 24 hours for onion root tips to complete the cell cycle, calculate the
average time spent in each phase as follows and record answers in your table. Place these values in the
table.
Stage of Mitosis
Number of Cells
Percentage of time
in each stage
Time spent in each
stage assuming 24
hour Cell Cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total Cells Viewed
Analysis of Results:
1. What is the cell cycle?
2. Briefly describe the events that occur during each of the four stages of mitosis.
3. Describe what happens to each of the following during mitosis. Indicate the phase(s) in which the
changes occur.
a. Nuclear membrane
b. Spindle fibers
c. DNA
4. GRAPH: Using your data, construct a pie graph of the onion root tip cell cycle showing the percent of
time spent in each stage. Provide a title and key for your graph.
5. Conclusion: Of all the stages of the Cell cycle, which stage do cells spend the most time in? Why?
HINT: Support your answer with the data you collected!