Laboratory
Observing the Cell Cycle of Onion Root Tip Cells
Background:
Because of their rapid growth, the cells of the root tips of plants undergo rapid
cell division. Ornamental onion root tips cells (aka Allium from the Plant Family:
Liliaceae (Alliaceae)) because of their accessibility and large cell size make excellent
specimens for the observation of mitosis—body cell division and interphase—the period
of time a cell spends in-between cell divisions. You are going to observe the preparation
of onion root tip cells using acetocarmine stain, and then, using prepared slides, identify
and photograph Allium cells in the various stages of mitosis.
Materials:
digital compound
light microscope
allium root tip
prepared slides
acetocarmine stain
Procedure:
Observation and photographing of Allium Root Tip Cells Using Digital Microscopes
Because of the superior quality of the cells in a prepared slide, we will use
prepared allium root tips slides to capture images of the different stages of the cell cycle.
Most of the cells that you observe will be in interphase. They are distinguishable because
they have no visible chromosomes. Cells in the various stages of mitosis are
distinguishable by looking at the position and state of their chromosomes (see Miller,
pages 246-247). Your job is to photograph at least one cell in each phase of the cell cycle:
interphase, prophase, metaphase, anaphase, telophase, and cytokinesis. For your
assessment for this lab, simply turn in the Procedure, and Analysis Questions and labeled
pictures of each of the phases of the cell cycle.
Procedure Questions:
1. Why are root tip cells used in this experiment?
2. What is mitosis?
3. What is the goal of mitosis?
4. What part of the nucleus of the cell is visible while the cell is dividing?
5. In what stage of the cell cycle does a cell spend most of its time (Hint: What stage do
you see the most of under the microscope?)?
6. Complete the statement: Mitosis occurs in SOMATIC or GAMETE (Circle 1) cells?
Results: Format your pictures to fit the following spaces and provide a description or
explanation of the stage.
Interphase
Description
Prophase
Description
Metaphase
Description
Anaphase
Description
Telophase
Description
Cytokinesis
Description
No Picture
Necessary Here
Analysis Questions:
1. In what stage does a cell spend most of its time?
2. Were you able to observe cells in all of the stages of the cell cycle? State some of the
biggest challenges in this experiment.
3. What are the stages of the cell cycle? How are they different from the stages of
mitosis?
4. Why do chromosomes pair during mitosis?
5. Does mitosis produce somatic cells or gametes?
Procedural elements of this lab were adapted from A Sourcebook for the Biological Sciences. Third edition. by Evelyn Morholt and
Paul F. Brandwein. Orlando, FL. Harcourt Brace & Company. 1986.