General Biology
Name___________________________________________________ Block _____________
Observing Mitosis in Onion Root Tips
As cells get bigger, they need to stop growing, divide, or die. If a cell divides, the two resulting daughter
cells need to be exact copies of the original parent cell. This requires the two daughter cells to have
the exact same DNA as the parent cell. DNA can be in one of two forms, chromatin or chromosomes.
Chromatin is unwound DNA and looks a bit like a bowl of spaghetti. On the other hand, DNA in the
chromosome form has a definite rod shaped structure. The part of the cell cycle that is responsible for
sorting and distributing chromosomes is called mitosis.
The cell life cycle has six distinct steps, but mitosis only represents four of these steps. Use your
notes and textbook to help with the details of each step. For this investigation you will need a slide
viewer and a slide strip with its accompanying booklet.
Pre­lab questions:
1. List at least two reasons why we need mitosis to happen in our bodies everyday.
a.
b.
2. Draw one chromosome and label the following parts: Chromosome, chromatid, and
centromere.
3. Write a brief description of what is happening to the DNA or chromosomes in each part of the
cell cycle
a. Interphase
b. Prophase
c. Metaphase
d. Anaphase
e. Telophase
f.
Cytokinesis
General Biology
Procedures and Analysis
1. 1. Set up your viewer with your slide strip on
slide #1. Have the slide booklet handy.
2. Start by finding a cell in its resting state or
interphase. Draw only that one cell in the
space provided, nice and big with the label
interphase. The more accurate you are with our
sketches the better!
3. Describe the contents of the cell’s nucleus in
interphase. Do you see rod shaped
chromosomes or spaghetti like chromatin?
4. What very important process happens to the
DNA during Interphase?
5. Locate a cell in prophase. Sketch and label
that cell.
6. Are chromosomes present in prophase? If
so, where are they in the cell?
7. What is happening or has happened to the
nucleus in prophase?
8. Locate a cell in metaphase. Sketch and label
that cell.
9. Where are the chromosomes located in
relationship to the cell membrane?
10. What is the name of the organelle that is now
present and really only functions during mitosis?
11. What is the name of the fibers that are now
present that are associated with the centrioles?
12. What is the responsibility of the mitotic
spindle?
Sketch of ONE cell in each phase and your
analysis for each phase
General Biology
13. Locate a cell in anaphase. Sketch and label
that cell.
14. What has happened to the chromosomes?
15. In what direction are the chromatids being
pulled?
16. What structure is responsible for separating
the chromosomes into chromatids?
17. Locate a cell in telophase. Sketch and label
the cell.
18. What seems to be happening to the
chromosomes?
19. What is or should be happening to the cell
membrane and cell wall?
20. What structure is probably starting to
reappear?
21. Locate a cell that has just gone through
cytokinesis. Sketch and label the two daughter
cells.
22. How do these two cells compare to any other
cell in interphase?
23. How does the number of chromosomes
found in the daughter cells compare to the
number found in the original parent cell?
Please clean up your viewer and slide strip and continue with the online portion of the lab.
General Biology
Onion Root Tip and Mitosis Online Activity
Go to the following website:
http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html
Read the information on each page and then click NEXT until you reach the mitosis activity.
Complete the following data table once you have finished the mitosis activity.
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total
number of
cells
36
percent of
cells
100%
1. Calculate what percent of the life cycle a cell spends in Mitosis compared to interphase.
2. Describe the main difference between plant mitosis and animal mitosis.
3. What are two reasons for mitosis to occur in multicellular organisms?
4. What is the purpose of mitosis in unicellular organisms?