Exploration Guide: Cell Division

Exploration Guide: Cell Division

Vocabulary: cell, mitosis, cycle, cell-division, interphase, DNA, prophase, metaphase, anaphase, daughter phase, chromosome, chromatin, chromatid, telephase, cytokinesis, sequence

Prior Knowledge:

Describe a cycle

Describe sequenc

If I have one large candy bar and break it in half I will have ___ candy bars. If I break those candy bars in half, I will have _____ candy bars. When those candy bars are broken in half I will have _____ candy bars.

Gizmo Warm-up:

• To set a slider to a specific number, type the number in the field to the right of the slider and hit Enter.
• Or move the slider

The lifespan of an individual cell can be divided into several stages that make up the cell cycle. In this activity, you will examine this sequence.

1. In the Gizmo™, set the Cycle Length to 5 hours. Click Play and observe the cells in the simulation.
2. After about 40–50 (simulated) hours, click Pause. How many cells were present at the start of the simulation?

1. How does the number of cells change over time?

1. Again click Play, and check Magnify. Now, as you mouse over the cells in the simulation you can see a magnified image of any cell.
2. Let the cursor rest for a while on a single cell and describe briefly what you observe as the simulation runs.

1. How many different cell appearances do you observe?

• To set a slider to a specific number, type the number in the field to the right of the slider and hit Enter.
• Or move the slider
• Click Pause. With Magnify still checked, examine several cells by mousing over them.

1. Sketch the different appearances these cells.

1. Using the DESCRIPTION pane to note the different stages of the cell cycle. Use the arrows to get information about the stages of mitosis.

1. List the phases.

1. Label your sketches of the cell you drew according to each of the ______stages.

1. What’s the sequence of the phases?

1. Why is it called a cell CYCLE?

• Be sure the DESCRIPTION pane is visible. Click the right arrow once, and read the material about the various stages.

1. What process relating to the cell's DNA occurs during interphase?

1. Why is interphase process so important?

1. Click the right arrow to display information about prophase. Prophase is the first stage of mitosis, the process by which a single cell becomes two identical ______.
2. What structures appear during prophase?
3. What structures disappear?

1. In prophase, the ______ are formed from the tangled strands of DNA called ______.
2. What three parts make up a single chromosome?
3. Click the right arrow to display information about metaphase. What events occur during metaphase?
4. Click the right arrow to display information about anaphase. Briefly describe the events that take place during anaphase.
5. Suppose the cell began with a total of 46 chromosomes, as human cells do. At the completion of this phase, how many chromatids are there at each pole of the cell?
6. How do the chromatids at one pole compare to those at the other?
7. Click the right arrow to display the information about telophase. Read that information. In the ______th and ______stage of ______the nuclear ______forms around the sets of ______. In telophase A ______appears in each ______and the ______unwind into ______.

• Be sure the DESCRIPTION pane is visible. Click the right arrow once, and read the material about the various stages.

1. What three stages make up interphase?

2. What happens in each stage?

• Click Reset. Set the cycle length to 12 hours.
• In this activity, you will estimate the relative duration of each phase of the cell cycle.

Relative Duration of the Phases

Click Play. Let the simulation run for about 100 (simulated) hours. Select the ABLE tab, and click Record Data. The table displays the number of cells that are in each of the phases at that instant. (Note that there are 100 total cells in the simulation now.)

1. Examine the table. How many of the cells were in each of the phases at that time?

2.Which phase had the largest number of cells?

3.With the simulation still running, click Record Data a second time. Which of the phases had the largest number of cells this time?

4.Which had the smallest number?

5.Click Record data two more times so that you have a total of four sets of data in your table. Based on these four recorded data sets, calculate the average number of cells in each of the five phases.

6.Which phase had the largest average number of cells?

7.What can you conclude about the amount of time that cells spend in this phase?

8.Which phase had the smallest average number of cells?

9.What can you conclude about the amount of time that cells spend in this phase compared to the other phases?

10. The percentages of cells in each phase reflects the amount of time that a given cell spends in each of the phases. For example, if 10% of the cells you found were in prophase, and the cell cycle was 12 hours long, then you would expect prophase to last about 1.2 hours.

Based on your data, how long does an average cell spend in each of the six phases of the cell cycle?

11. What part of mitosis takes the longest amount of time?

12. The shortest?

13. Why do you think this is?

14. In humans and most other living things, the duration of the cell cycle is closely regulated. What do you think would happen if cell division occurred in an uncontrolled way? If possible, discuss your ideas with your classmates and teacher.