Mitosis Lab

Objectives

1. Prepare a slide of stained chromosomes using the squash technique.

 

2. Identify the stages of mitosis from prepared stained slides of onion root tips seen under the compound microscope.

 

3. Identify the structures visible under the compound microscope of cells in various stages of cell division.

PROCEDURE

Each human originates with the fertilization of an egg. At this stage of development the individual consists of a single cell about the size of the period at the end of this sentence. Division of this cell and many divisions of sequential cells over a period of several years, may result in the formation of an adult human, consisting of about 1018 cells. Among these are cells of many kinds, each having a different structure, function, and life span. This process of mitosis, cell division, continues as long as the human or parts of his body are alive.

 

In this investigation you will see the cell in the various stages of mitosis. I. Staining Chromosomes

Procedures:

1. With forceps, place an onion root tip in the center of a clean slide. Using a scalpel or razor blade, cut off the terminal cm of the tip of the root. Dispose of the rest of the root.

2. Cover immediately with 3 or 4 drops of the 1N HCl. The acid is to act on the root tip for 5 minutes. During this period the slide is to be heated gently. This is done by placing the slide on the diffused light source for 5 to 7 minutes. The onion root tip must be covered with the HCl solution during this warming period.

 

3. Blot off the acid without touching the root tip and cover the root tip with 2 or 3 drops of the toluidine blue solution. The stain is to set for about 5 minutes and is to be warmed in the same manner as with the acid solution

 

4. Blot off the stain solution carefully. Add 2 drops of fresh stain solution carefully and add a cover glass.

 

5. With the slide flat on the table, place your thumb on the cover glass exactly above the specimen. Press straight down hard.

 

6. Blot the back of the slide and examine on low power. Look for embryonic cells. They appear square. When you find mitotic figures, switch to high power.

III. Draw and label cells in interphase ,prophase, metaphase, anaphase, and telophase stages of mitosis from slides you prepared.

STAGES OF MITOSIS By definition:

Prophase         begins when chromosomes are visible with the light microscope and contin­ues until the nuclear membrane is no longer visible.

Metaphase begins when nuclear membrane is no longer visible. Chromosomes are in mass in the center of the cell.

Anaphase        begins when the identical chromosomes start moving toward opposite ends of the cell.

Telophase       begins with the invagination of cell membrane in animal tissue and with the first visible evidence of a forming cell plate in plant cells.

Interphase chromosomes not visible with light microscope (not a stage of mitosis).

 

 

 

1. Describe the prominent cell morphology as seen through the compound microscope of animal tissue in each of the following phases:

Interphase

 

 

 

 

 

 

anaphase

Prophase

 

 

 

 

 

 

telophase

Metaphase

 

 

 

 

 

 

 

 

2. Normal cell functions such as protein synthesis and respiration occur during which phase?

3. The duplication of DNA and chromatids occurs during which phase?

4. If a parent cell has 32 chromosomes, then after mitosis daughter cells each have how many chromosomes?

5. Contrast the telophase in animal and plant cells.