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Chapter 17 INVESTIGATIONS

NEL Cell Division 587

Frequency of Cell Division

In this activity, you will view and compare cells from onion

cells and from a whitefish blastula in various stages of mitosis.

Because slides are used, the cell divisions you will be viewing

are frozen in time. Therefore, it will not be possible for you to

watch a single cell progress through the stages of mitosis.

Based on your observations, you will determine the frequency

of cell division and construct a clock representing the division

cycle, given the time taken to complete one cycle of mitosis.

In a table, you will record the number of cells in each stage of

mitosis.

Materials

microscope prepared slides of onion root tip

lens paper prepared slides of whitefish blastula

Procedure

Part 1: Observing Dividing Cells

1. Obtain an onion root tip slide and place it on the
   stage of your microscope. View the slide under low-
   power magnification. Focus using the coarse-
   adjustment knob.

Chapter 17

Purpose Design Analysis

Problem Materials Evaluation

Hypothesis Procedure Synthesis

Prediction Evidence

INVESTIGATION 17.1 Report Checklist

smaller cells: an

area of rapid cell

division

long cells: not

an area of cell

division

Figure 1

Meristematic region of the onion root tip

where the cells are actively growing and

dividing

2. Centre the root tip in the field of view and then rotate
   the nosepiece to the medium-power objective lens.
   Focus the image using the fine-adjustment knob.
   Observe the cells near the root cap. This area is
   referred to as the meristematic region of the root.


3. Move the slide to view the cells away from the root tip.
   These are the mature cells of the root. Record the
   differences between the cells of the meristematic area
   and the mature cells of the root. Draw a diagram to
   help you (Figure 1).


4. Return the slide to the meristematic area and centre
   the root tip. Rotate the nosepiece to the high-power
   objective lens. Use the fine adjustment to focus the
   image.


5. Locate and observe cells in each of the phases of
   mitosis. It will be necessary to move the slide to find
   each of the four phases. Use Figure 1as a guide.
   Draw, label, and title each of the phases of mitosis.
   It is important to draw only the structures that you
   can actually see under the microscope.