Biology (Holt)

In plant cells and other cells that have rigid cell walls, the

cytoplasm is divided in a different way. In plant cells, vesicles

formed by the Golgi apparatus fuse at the midline of the

dividing cell and form a cell plate. A cell plate is a membrane-

bound cell wall that forms across the middle of

the plant cell. A new cell wall then forms on both

sides of the cell plate, as shown in Figure 11.When

complete, the cell plate separates the plant cell

into two new plant cells.

In both animal and plant cells, offspring cells are

about equal in size. Each offspring cell receives an

identical copy of the original cell’s chromosomes.

Each offspring cell also receives about one-half of

the original cell’s cytoplasm and organelles.

132 CHAPTER 6Chromosomes and Cell Reproduction

Forming

cell plate

Cell wall

Nucleus

Figure 11
Cytokinesis in
plant cells.A
cell wall forms
in the center of
the dividing cell.

Observing Mitosis and Cytokinesis

You can identify the stages of mitosis and the process

of cytokinesis by observing slides of tissues undergoing

mitosis using a compound microscope.

Materials

compound microscope, prepared slide of mitosis,

paper, pencil

Procedure

1.View a prepared slide of cells

undergoing mitosis under low

power of a compound micro-

scope.

2.Move the slide until you find a

section where different stages

of mitosis are visible.

3.Switch to high power. Use

the photos in Figure 9 to help

you locate and identify cells

in interphase and in each

stage of mitosis.

4.On a separate piece of paper,

sketch an example of each

stage. Label each sketch with

the following terms where

appropriate: chromosomes,

cell membrane, cytoplasm,

nucleus, spindle, and cell wall.

5.Switch to low power, and

estimate how many cells are

clearly in interphase and how

many cells are in one of the

stages of mitosis.

Analysis

1. Describe the activity of
   chromosomes in each stage
   of mitosis.


2. Compare the number of
   cells in interphase with the
   number of cells in one of the
   stages of mitosis.
   3.Critical ThinkingInfer-
   ring RelationshipsWhat
   does your answer to item 2
   indicate about the relative
   length of interphase?

Describethe function of the microtubules

during anaphase. 4B 6E

Describethe events that occur during each of

the four stages of mitosis. 4B 6E

Comparehow cytokinesis occurs in plant cells

with how it occurs in animal cells. 4B 6E

Mitosis could not proceed if a

mutation interrupted the assembly of

Athe cell wall. Cthe cell membrane.

Bspindle fibers. Dthe nuclear envelope.

TAKS Test PrepTAKS Test Prep

Section 3 Review

4B 6C