Anatomy and Physiology I Fall 2000
Lab Session 3

Cell Structure and the Cell Cycle


Name _________________________ Exit Quiz ______
File # _______

Introduction

The cell is the basic unit of structure and function of living organisms. Many of the functions of cells are performed by particular sub-cellular structures called cell organelles. The life cycle of a cell is described by the cell cycle. Cells in many parts of the human body divide to produce more cells of the same type. The hereditary information contained within the nucleus of a parent cell must first be replicated and then evenly distributed between the resulting daughter cells through mitosis or meiosis. The cell division of the parent cell into daughter cells is called cytokinesis. In this lab we will investigate both the structures and functions of several cell organelles and the generalized cell cycle. Please read Chapter 3 pp. 46-56 and 65-71 in preparation for this laboratory investigation.



I. Cell Organelles

Be able to identify the following cell organelles/structures and their respective functions on diagrams and models. (Fig. 3.1 p. 46 text book)

Plasma membrane
phospholipids
phosphate groups
fatty acids
Cytoplasm
Cytoskeleton
microtubulus
microfilaments
Centrosome
Centriole
Rough and smooth endoplasmic reticulum
Golgi apparatus
Lysosome
Mitochondrion
Ribosome
Nucleus
nuclear envelope
nuclear pore
chromatin
nucleolus

Questions Section
Label the lab handout of the generalized animal cell and attach to lab report.






II.The Cell Cycle
A. Be able to identify and/or draw the following stages of the life cycle of a cell
(Fig. 3.29 p. 68; Fig. 3.31 p. 69; Fig. 3.34 p. 72 text book)

Interphase
G1 phase
S phase
G2 phase
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Meiosis
Prophase I and II
Metaphase I and II
Anaphase I and II
Telophase I and II
Cytokinesis I and II


B. Lab Procedure

a. Prepared Microscope Slide - Whitefish Blastula Mitosis

1. Obtain a prepared slide of Whitefish Blastula Mitosis.

2. Using the scanning objective focus on the whitefish blastula cells and identify a cell undergoing mitosis by looking for dark-staining bodies (chromosomes) within the cell.

3. Switch to the low-magnification10X objective and fine-focus.

4. Switch to the high-magnification 40X objective and fine-focus. At this magnification you should be able to identify cells in several stages of mitosis. Identify a specific stage of mitosis and go on to step 5.

5. Add a dop of oil to your prepared slide and switch to the oil-immersion 100X objective and fine-focus.

Questions Section
1. Repeat steps 4 and 5 for all four stages of mitosis. Draw the observed stages of mitosis in the questions section of the lab report. Label each drawing for the stage of mitosis.

2. Label the lab handout of the stages of mitosis and attach to lab report.




b. Preparing your own microscope slide - Onion Root Tip
CAUTION: the following procedure involves the use of solutions which are either acidic or stains. Exercise due care when using any of the solutions.


1. Pour approximately 5 ml. methanol-acetic acid fixative into a small beaker. Place 2-3 mm length onion root tip into the fixative. Incubate at 60 C for 15 mins.

2. At the end of the fixative incubation period, pour off the fixative into a waste beaker. Be careful not to pour off your fixed onion root tip. Now add approximately 5 ml. 1 M HCl to your fixed onion root tip to partially hydrolize the cells. Incubate at 60 C for exactly 10 mins.

3. At the end of the hydrolysis incubation period, pour off the 1 M HCl into a waste beaker. Be careful not to pour off your fixed/hydrolyzed onion root tip. Now add approximately 1 ml. Feulgen stain to your fixed/hydrolyzed onion root tip in order to stain the chromosomes. Bath your onion root tip in the Feulgen stain for 20-30 mins. to allow the Feulgen stain to penetrate the chromosomes.

4. To make a slide of your stained onion root tip, transfer your onion root tip from the beaker to a microscope slide and add a small drop of 45% acetic acid. Do not allow the onion root tip to dry out during the subsequent steps. Add 45% acetic acid if you notice your specimen is drying out.

5. Pulverize your onion root tip into a fine pulp on the microscope slide by tapping it with a glass rod. Try to produce as fine a pulp as possible to prevent large cell clumps which will not be useful for microscopic examination.

6. Now place a microscope cover slip on top of your pulverized onion root tip. Put two layers of paper towel on top of the microscope cover slip and press hard. This should result in the onion root tip cells from forming a monolayer which is ideal for microscopic examination.

7. Using the scanning objective focus on the onion root tip cells and identify a cell undergoing mitosis by looking for pink-staining bodies (chromosomes) within the cell.

8. Switch to the low-magnification10X objective and fine-focus.

9. Switch to the high-magnification 40X objective and fine-focus. At this magnification you should be able to identify cells in several stages of mitosis. Identify a specific stage of mitosis and go on to step 10.

10. Add a dop of oil to your prepared slide and switch to the oil-immersion 100X objective and fine-focus.

Repeat steps 9 and 10 for all four stages of mitosis. As part of your Lab Exit Quiz you will be asked to:
1) show your prepared onion root tip slide to a lab instructor under the microscope.
2) identify several stages of mitosis on your prepared onion root tip slide.






Questions

1. Label the lab handout diagram of the generalized animal cell. Attach this sheet to your lab report. (10 pts.)


2. Label the lab handout diagram of the stages of mitosis. Attach this sheet to your lab report. (10 pts.)


3. Describe what happens in the following stages of mitosis: (8 pts.)
a. Prophase



b. Metaphase



c. Anaphase



d. Telophase




4. Below draw the chromosome arrangements as observed at 100X magnification for each of the four stages of mitosis for the prepared slide of whitefish blastula. Make sure you clearly label each stage of mitosis. (12 pts.)