Name
Period
Cell Division Lab
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. These carrot cells are
dividing for growth. Other reasons cells divide include, repair or replacement.
Problem
How long to the stages of the cell cycle take?
Skills
Observing, calculating
Materials
Microscope
Drawings of cell phases
Calculator
Prepared Onion Root Tip slides
Procedure
1. Get one microscope slide and carry it to your microscope with two hands.
2. There will be three root tips on a slide. Hold the slide up to the light to see the pointed ends of the root
sections. This is the root tip where the cells WERE actively dividing.
3. Place the slide on the microscope stage with the root tips pointing away from you. Center the root tips on
the stage. Using the low power objective to find the root tip, and focus with the course adjust until it is
clearly visible. Just above the root “cap” is a region that contains many new small cells. Once the root tip
is in focus move the stage toward the root tip. The cells of this region were in the process of dividing when
the slide was made. Center the image close to the root tip and switch to higher power and focus using the
fine adjustment knob.
4. Move the objective to 40X power and focus using ONLY THE FINE ADJUSTMENT KNOB>
5. Use the book to label each phase – or your memory!
6. Looking along the rows of the cells, identify the cell
division stage each of the cells.
7. Use the data table on the next page to record the
number in the field of view that are in each stage.
The easiest way to do this is for one partner to look
through the microscope going along each column of
cells and counting the phases one at a time. For
interphase, you may want to count ¼ of the field of
view and multiply by 4.
8. Next, count prophase, metaphase, anaphase and
telophase.
9. Once you complete the data for one field of view,
switch to another onion root tip on the same slide
and have the second person count the cells. Record
these numbers under sample 2 in the data table.
10. Add the two numbers for each stage of mitosis and
interphase to determine the total number.
11. Use the calculation to determine the minutes spend
in each stage of mitosis.
DATA TABLE: Cell Division in Onion Root Cells
Stage of the Cell Cycle
First
Second
Sample
Sample
Interphase:
Mitosis:
Prophase
Metaphase
Anaphase
Telophase
Total Mitosis
Total Time In Cell Cycle
Total Number
Total Time
(Minutes)
% of cells in
stage
ANALYZE AND CONCLUDE- RSQ
1. What is the goal of mitosis?
The goal of mitosis is to make
2. What are the three reasons cells divide?
3. Calculating: The cell cycle for onion root tips takes about 720 minutes (12 hours). Use your data and
the formula below to find the number of minutes each stage takes. Record in the table
Time for each stage = Number of cells at each stage x 720 minutes =
Total number of cells counted
4. Calculating: Determine the % of cells in each stage of the cell cycle
Total Number in Phase from column 3
X 100 =
%
Total Number in cell cycle
minutes
5. Observing: Which stage of the cell cycle did you observe most often?
6. Communicating: Use the data (that means numbers!!!!!!) to compare the amount of time spent in
interphase versus mitosis with the total time for the whole cell cycle (720 minutes). Write your answer
in a paragraph. Should be 4 to 5 sentences. RSQ
7. Why are there intermediate stages? (Some might look like they are in between phases). What does
this suggest about the cell cycle?