Procedures:

Mitosis in Onion Root Tips

Mitosis in plants occurs in localized areas known as meristems. The tip of the shoot and tip of the roots are two of the areas where meristems occur. The root tip is covered with a protective sheath, the root cap.  The meristem is several layers of cells away from the tip of the root cap.

Materials

Used by permission from http://www.microscopy-uk.org.uk/micropolitan/botany/frame4.html

Examine the root tip slide photograph taken with the 4X lens.

Used by permission from https://molgen.osu.edu/

Question: Can you distinguish any cells?_____________________________________________________________Are some cells longer than others? __________________________________________________________________________________________________________________________Looking near the root tip (but not at the root cap) can you see any cells in the process of cell division? _____________

Used by permission from https://molgen.osu.edu/8. Identify as many of the stages of mitosis as you can. Make a sketch of a representative cell in each of the four stages of mitosis in the space provided on your lab report form.

9. Go to http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html and complete their online activity. Complete the chart in your lab report form as you go.

If you were to assume that the number of cells in a phase indicates the time spent during mitosis of that phase, then you could infer that the phase with the largest numbers of cells would take longer and that the phases with the fewest numbers of cells would be fastest. Time spent in a phase could then be calculated, because it is known that the time for a typical onion cell to complete mitosis is 16 hours (960 minutes), from interphase to interphase. We can calculate the percentage of cells in each phase by dividing the number of cells in a phase by the total number of cells counted.

Example: If your table indicates that 8 out of the 36 total cells observed were in anaphase, then

8/36 = .22.22 x100 = 22 %

of cells are in anaphase. Calculate the amount of time spent in each phase of the cell cycle from the percent of cells in that stage. (Multiply percentage of time in phase times the number of minutes in the cell cycle).

Example:

22 % x 960.22 x 960= 211. 2

211.2 minutes spent in anaphase.

10. Use http://nces.ed.gov/nceskids/createagraph/ or Excel to create a pie graph of number of minutes spent in each cycle. If you cannot use either program, you may draw the graph.

Mitosis in Animal Cells

Telophase and CytokinesisWhitefish is a commonly employed organism for study of animal mitosis.

Interphase

Prophase

Metaphase

Anaphase

Telophase

Telophase and CytokinesisWhitefish is a commonly employed

organism for study of animal mitosis.

Materials

Photographs of prepared slides of whitefish

http://biog-1101-1104.bio.cornell.edu/BioG101_104/tutorials/cell_division/wf_review_fs.html

1. Examine the photographs of whitefish mitosis and observe the sliced blastula (discs) of Ascaris and sketch cells in each stage of mitosis in the space below.

Question: Summarize the differences between mitosis in plants and animals.

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Modeling the Stages of Mitosis

*Note: This section is highly recommended, but not

mandatory.

Often, modeling can help us break a process down into essential components and sequences. Mitosis is one such process. We will use a set of pop beads to simulate the appearance of a cell as it progresses through the stages of mitosis. Before beginning this part of the lab, view an animation of mitosis.

Materials

• Pop Beads, red and yellow• 4 rubber stoppers (approx. 1 inch dia.)• Yarn (Red and Yellow)• Small Beads• White string1. After viewing the animation of mitosis, you will use the pop beads to examine the events and phases of mitosis.

2. Obtain:

• 20 red beads and 20 yellow beads• 8 rubber-tipped magnets• 2 feet of red yarn and 1 foot of

yellow yarn (you may have to cut this yourself)

• 4 of the cylindrical beads• 2 3-inch short pieces of red yarn• 2 3-inch short pieces of yellow

yarn• 2 10-inch long pieces of red yarn• 2 10-inch long pieces of yellow

yarn• 2-3 feet of white string (you may

have to cut this yourself)3. Assemble four “chromosomes” as follows:            a. Place one red

bead in each end of a rubber-tipped magnet            b. Place one yellow bead in each end of a rubber-tipped magnet            c. Place 5 red beads in each end of a rubber-tipped magnet            d. Place 5 yellow beads in each end of a rubber-tipped magnet

4. Arrange the 2-foot long piece of red yarn into a circle and place it on your lab bench.

5. Arrange the 1-foot long piece of yellow yarn into a circle and place it inside the red yarn circle already on the table.

6. Place one each of the short yellow, short red, long yellow, and long red pieces of yarn on the table inside the yellow yarn circle.

7. Place the rubber stopper inside the red yarn circle.8. Place two of the cylindrical beads inside the red circle (but just outside the yellow circle)

Question: What do each of the pieces on the table before you represent in a real cell?

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9. Simulate the events of prophase by adding or removing material from the yarn circles on your desktop. Draw the cell as it appears in prophase in the space below:

10. Simulate the events of metaphase. Draw the cell as it appears in metaphase in the space below:

11. Simulate the events of anaphase. Draw the cell as it appears in anaphase in the space

below:

12. Simulate the events of telophase. Draw the cell as it appears in telophase in the space below: