Name: ___________________________________________ Date: _________________ Period_______
Cell Cycle Prediction Lab (40 points)
Hypothesis: Based on what you know about the events that occur in the stages of the cell cycle, which stage do
you think the cell spends most of its time in? (4 points)
This should be as detailed as possible. A possible answer could be: Due to the fact that DNA replication occurs
during interphase, the cell will spend most of its time in interphase.
Materials:
-1 Onion root tip
-1 pair of forceps
-1 compound light microscope
-Pipette
-Protractor
-1 microscope slide
-1 coverslip
-Water
-Calculator
Procedure:
1. In your groups, you will first prepare a microscope slide with an onion root tip using the following steps.
a. Add 2 or 3 drops of water to the microscope slide using the provided pipettes.
b. Peel a section of the root tip from the onion and peel off any membrane that you can.
c. Gently place the root tip on the slide so that it lays flat in the water.
d. Slowly lower a cover slip over the root tip and the water so that no bubbles form under the
coverslip making sure to keep the onion root flat.
e. Slide the coverslip around gently to remove any bubbles that may become trapped.
2. Observe your onion root slide beginning with the lowest objective lens of the microscope.
3. Zoom in and move into the viewing area the section of the root tip that you want to study. Make sure
you can see cells of different stages in the section you choose.
4. Count the number of cells in the microscope view and record the total.
5. Identify the number of cells in each phase of the cell cycle within your viewing range and fill in Table A
below.
6. Calculate the percentage of cells that are in each phase and then determine how many hours a day
(remember there are 24 hours in a day) the cell spends in that stage.
7. In the space provided draw a pie graph that demonstrates how much time the cell spends in each phase.
Data (10 points):
Interphase Prophase
Metaphase Anaphase Telophase Cytokinesis Total
Number of Most cells The second The rest
Will vary
cells
should be
highest
will vary,
because
in
number
but should
students
interphase should be
be similar
will have
in prophase to one
different
another
roots
Percent of Number of Number of Number of Number of Number of Number of
cells in this cells in
cells in
cells in
cells in
cells in
cells in
100%
stage
interphase/ prophase/ metaphase/ anaphase/ telophase/ cytokinesis/
total
total
total
total
total
total
number of number of number of number of number of number of
cells
cells
cells
cells
cells
cells
How many 24 hours x 24 hours x 24 hours x 24 hours x 24 hours x 24 hours x
minutes
percent in percent in percent in percent in percent in percent in 1 day (1,440
spent in this this stage
this stage
this stage (as this stage
this stage
this stage
minutes)
stage
(as decimal) (as decimal) decimal)
(as decimal) (as decimal) (as decimal)
Name: ___________________________________________ Date: _________________ Period_______
Data Representation
What type of graph will you use to represent the data you collected in the table? _______________________
In the space below, draw your representation of the cell cycle data. You may use a protractor. (10 points)
Students will draw their pie charts of the cell cycle here. Results will vary by group. The percentages should be
close to those described in the table above.
Post-Lab Questions
1. When you are done with the lab and have answered the above questions, look in the book at an actual
drawing of the cell cycle. Is your drawing accurate? What is the same and what is different about the two?
(4 points)
If your book does not have a good image of the cell cycle, you may project the cell cycle to the students
when they are done with their graphs. A good image can be found at this website:
http://www2.le.ac.uk/departments/genetics/vgec/schoolscolleges/topics/cellcycle-mitosis-meiosis.
2. In what stage does the cell spend the majority of its time? Does this finding support your initial hypothesis?
(2 points)
The answer should be interphase. Whether or not it supports the hypothesis will vary by group.
3. Why do you think the cell spends most of its time in this stage? What is occurring during this stage and why
is this event so important to successful asexual reproduction (cell division)? (5 points)
Interphase is the stage in which the cell is performing its normal functions. The organism needs these cells
to perform these functions so it makes sense that this would be the longest phase. Also, and most
importantly to cell division, it is during interphase that the DNA is replicated. In asexual reproduction (or
mitosis), the number of chromosomes must remain the same in each daughter cell because the cells must be
identical. In order for this to happen, the chromosomes must double to keep chromosome number the same
in both daughter cells. This process of such high importance should be given time to happen accurately and
for the many checks to happen.
4. Does this process always work? No (1 point)
5. What do you think would happen to the cell if the processes in this stage do not happen correctly or happen
at all? (4 points)
If the DNA did not replicate properly, at least one of the daughter cells will be left with an incomplete sert
of DNA and will probably be unable to perform many of the cells necessary functions. This is why
interphase and DNA replication are so important before cell division.