Name: ________________________
Date: _____________
Observing Mitosis in Onion Root Tip
Background:
The cell cycle is the sequence of growth and division that occurs during the life cycle of a cell.
There are four major phases to this continuous process. The first phase is G1 (Gap 1) which is where the
cell grows. The S phase (Synthesis) is the phase where DNA replicates. The G2 phase (Gap 2) is where
the cell continues to grow, makes new organelles, and prepares for division. The M phase is the final
phase of the cell cycle
which consists of
division of the nucleus
and cytoplasm.
The division of
the nucleus is called
mitosis. Mitosis is
broken down into four
major phases:
prophase, metaphase,
anaphase, and
telophase. At the end
of mitosis the genetic
material of the original
parent cell has been
divided equally into two
nuclei. This is followed
by cytokinesis the
division of the
cytoplasm and its
organelles. The end
result of mitosis and cytokinesis is the formation of two new identical cells from a single parent cell.
In this activity, you will observe the process of cellular division in plant cells. In a growing plant
root, the cells at the tip of the root are constantly dividing to allow the root to grow. Because each cell
divides independently of the others, a root tip contains cells at different stages of the cell cycle. This
makes a root tip an excellent tissue to study the stages of cell division. Onion root tips are extremely
popular for viewing the different phases of mitosis because the chromosomes are large and very dark
when stained. Working in groups of two, your task is to observe and identify the different stages of
mitosis in the onion root tip.
Question: When looking at an onion cell will there be more cells in one phase than the others?
Observation:
Hypothesis:
Materials:
 Microscope
 Onion root tip prepared slide
 Colored pencils
Procedure
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Place onion root tip slide on microscope.
Using the lowest power objective and the coarse adjustment knob, bring the specimen into focus.
Move the objective to the next power and using the fine adjustment knob, bring into focus.
In your field of view determine (count) how many cells are showing Interphase, put this number in
the data chart.
Determine how many cells are showing Prophase, put this number in the data chart.
Determine how many cells are showing Metaphase, put this number in the data chart.
Determine how many cells are showing Anaphase, put this number in the data chart.
Determine how many cells are showing Telophase, put this number in the data chart.
Add up each column and determine the average number for each phase. Put this in the data
chart.
Construct a graph showing the average number for each phase. Be sure to include the
independent variable, dependent variable, legend, and title.
Observation & Data:
Mitosis Phases
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total # in
each phase
Average # in
each phase
(total/6)
Analysis:
Create a graph showing the average number of cells counted in each phase. Be sure to label the
independent and dependent variables, and create a title.
Conclusion:
Write a paragraph, which explains the results of this experiment using the concept of Mitosis. Your
paragraph should include the bullet points from the writing a lab report handout/foldable in your
notebook.
Post Lab Questions
1.
Which stage of the cell cycle are most of the onion root tip cells from your data? Explain why most cells
are seen in this stage.
2. Which stage has the lowest percentage of cells from your data?