Where is Mitosis Most Common?
Casondra Gregory
Biology
Ms. Carpenter
February 26, 2013
Problem, Hypothesis, and Prediction
The problem in the lab was to investigate whether mitosis occurs at the same
rate in all of the parts of an onion root. The hypothesis is that mitosis will not occur
at the same rate in the parts of the onion root. The prediction for the experiment is
that there will be more cells in interphase and prophase than metaphase, anaphase,
or telophase.
Materials
 Slide of onion root tip
 Microscope
 Pipet
 Pencil
 Water
 Forceps
 Paper towel
 Scalpel
 HC fluid
 Toluidine blue
 Carnoy fluid
 Coverslip
 Paper
 Two small cups
Procedure
To locate area X, first place the onion root tip slide on the microscope and
make sure it is on low power. Area X should be located at the lower end of the root
tip near the center. Once you have found area X, switch to high power. Next,
identify the cells that are in mitosis and interphase. Create a data table and record
the number of cells observed in each phase of mitosis and interphase.
To locate area Y, first switch the microscope back to low power. Area Y
should be located farther up the root tip on the right side. Once you have found
area Y, switch the microscope to high power. Next, identify the cells that are in
each phase of mitosis and interphase. Record in the data table the number of cells
observed in each phase of mitosis and interphase.
First, get two cups and label one HCI and the other Carnoy. Pour enough
HCI in the cup labeled HCI to cover the bottom, and enough Carnoy in the cup
labeled Carnoy to cover the bottom. Next, use forceps to transfer an onion root into
the cup labeled HCI. After 4 minutes, transfer the root into the cup labeled Carnoy.
Leave the root in the Carnoy for 4 minutes. After 4 minutes, place the root on a
slide. With a scalpel, cut off 1-2mm of the root tip, and keep only this tip. Cover
the root tip with a few drops of toluidine blue for 2 minutes. After 2 minutes, blot
away the stain without touching the tip. When the stain has been blotted away,
cover the tip with 1-2 drops of water, and gently put a coverslip over the root tip.
Cover the slide with a piece of paper towel and press firmly on the coverslip.
Observe the slide under the low power of a microscope. Using the low power,
observe the slide to find cells of various stages of division. Once you have located
a cell, change to high power. Try to observe several cells in each stage.
Data
Area X
Interphase
Prophase
Metaphase
Anaphase
Telophase
Area Y
60
10
4
7
1
Area Z
63
13
6
4
3
45
15
4
3
2
Telophase Area X
Anaphase 1%
Metaphase 9%
5%
Interphase
Prophase
Prophase
12%
Interphase
60
73%
Metaphase
Anaphase
Area Y
Anaphase
Metaphase 4%
Telophase
3%
Interphase
7%
Prophase
Prophase
15%
Metaphase
Interphase
71%
Anaphase
Telophase
Area Z
Anaphase Telophase
3%
Metaphas 4%
e
6%
Prophase
22%
Interphase
65%
Interphase
Prophase
Metaphase
Anaphase
Calculations
60/82=.73=73%
Analysis and Conclusion
The lab was done to show interphase and the different phases of mitosis in
an onion root tip. Areas X,Y and Z were all looked at to determine how many cells
were in each stage of mitosis and interphase. The cells in Area X were looked at
first through the microscope, and then Area Y. To find area Z, the onion root tip
was transferred into a cup of HCI fluid for 4 minutes, and then into a cup of
Carnoy for 4 minutes. Then, 1-2mm of the root tip was cut off, and only this tip
was kept. The root was then covered with toluidine blue for 2 minutes. Then the
slide was covered with a coverslip and a paper towel was pressed on it. Last, the
slide was observed under the microscope for the phases of mitosis and interphase.
An analysis of the data showed that there was almost an equal number of
interphase in all three areas, but area Z had the least, with 28%. There was also
almost an equal number for prophase, but area Z had the most, with 40%. 50% of
all the anaphase found was in area X, and the three areas had almost an equal
number of metaphase and telophase.
Errors that could have occurred in the experiment were the counting of the
interphase, prophase, metaphase, anaphase, and telophase. Some of the phases
were hard to identify, and this could have affected the experiment by the numbers
of each phase not being correct. Another error that could occur while doing the
experiment is looking at the phases in one area, going to another area, and then
trying to go back to the first area. This could be a problem in the experiment
because it may be hard to try and find the exact location the first area was at.
Questions/Answers
1. Which area of the onion root tip(X, Y or Z), had the greatest percentage of
cells undergoing mitosis? The lowest? Use specific totals from your data
table to support your answer.
Area Y had the greatest percentage of cells undergoing mitosis. Area Y had
a total of 63 cells for interphase, Area X had 60 and Area Z only had 45.
Area Z had the lowest percentage of cells undergoing mitosis. For anaphase,
Area Z only had 3 cells, while Area Y had 4 cells, and Area X had 7 cells.
2. If mitosis is associated with rapid growth, where do you believe is the
location of most rapid root growth, area X, Y or Z?
I believe the location of most rapid root growth is area Y because it had the
greatest percentage of cells undergoing mitosis.
3. Where might you look for cells in the human body that are undergoing
mitosis?
You might look for cells in the human body undergoing mitosis in organs
and organ systems.
4. Assume that you were not able to observe cells in every phase of mitosis.
Explain why this might be, considering the length of each phase.
You might not be able to observe cells in every phase of mitosis because
some phases are longer or shorter than others. You might see more cells in
interphase because it is the longest phase of the cell cycle, and less cells in
metaphase, anaphase, or telophase.
5. What factors might cause misleading results? How could you avoid these
problems?
Factors that might cause misleading results are looking in the wrong area for
cells or not knowing what each phase looks like. You can avoid these
problems by making sure you are looking in the right areas, and knowing
what each phase looks like.
6. What are the possible discrepancies that could have or did occur in the data
when comparing the numbers of cells in each phase between the X and Z
samples?
Possible discrepancies that could have occurred are not doing the
experiment to find Area Z exactly right, so the numbers would not be as
correct as if you had done the experiment right. Another discrepancy is not
counting the phases right, or counting one phase for another.
7. What steps could you take to ensure that the next time you complete a lab in
class the accuracy of the data will be precise?
Steps you could to ensure the accuracy of the data will be precise is reading
the directions of the lab, and making sure that you know exactly what you
need to be doing. Another step to take is following all the directions, and
making sure you do not skip a step.