Observing Mitosis
Cells need to either stop growing or divide. 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 is can be in one of two forms, chromatin or chromosomes.
Chromatin is unwound DNA and looks a bit like a bowl of spaghetti. However,
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 your lab notebook, a slide viewer, and a
slide strip with its accompanying booklet. Please title this lab Observing
Mitosis.
Pre-lab questions:
1. List at least two reasons why we need mitosis to happen in our bodies
everyday.
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
 Interphase
 Prophase
 Metaphase
 Anaphase
 Telophase
 Cytokinesis
Procedures and Analysis
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 your lab notebook nice and big and label it. 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? Is 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 and that are
associated with the centrioles?
12. What is the responsibility of the mitotic spindle?
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 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.
Onion Root Tip and Mitosis Online Activity
Go to the following website:
http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.htm
l
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?