Investigation 16
What does the Nucleus do?
Introduction
Points:
|310
When discussing our survey of the cell organelles, we talked about the Nucleus. If you remember correctly, the
function of the Nucleus is to house the genetic material of the cell. However, what does the nucleus do with
that genetic material? What form is the genetic material in? What is the function of that genetic material?
Today, you will be observing the enlarged nucleus of the allium (onion) plant in an attempt to discern what
actually goes on in the nucleus.
Objectives
1. To determine what the actual function of the nucleus is.
2. To determine what form genetic material takes in the nucleus.
3. To determine what the actual function of the genetic material is.
3. To practice appropriate laboratory procedure.
Materials
Microscopes (virtual or tangible)
allium slides
Procedure
1. Obtain your materials. First you will be using the virtual microscope, and second the optical microscope.
To access the virtual microscope, go to the following address on a computer:
http://www.udel.edu/biology/ketcham/microscope/scope.html
2. The procedure for using the microscope is the same, either using the virtual or optical microscope.
Remember, this is how to produce a quality image:
*Move the stage to the lowest point, place the slide on the stage, and center the slide over the opening.
*Change the turret to the lowest power objective, and move the stage up to the top.
*Adjust the ocular distance (space between eye pieces) if necessary.
*Begin to focus on your specimen, using the coarse adjustment.
*As you begin to focus, you may need to use the mechanical stage to re-center your image.
*Once your image is in focus, you can switch to a higher power objective.
*When refocusing on higher power, remember only to use the fine adjustment.
3. Using the space below, draw the nuclei of six different (meaning that the cells are different) cells, you can
draw just the nucleus and what you find inside. Make sure to use color. (60 points)
4. What is the function of the nucleus? (10 points)
5. You may have noticed that some of the “worms” in the nuclei have a regular shape, draw a magnified view
of one single “worm” below. Use your imagination to magnify what you saw in the microscope. Use color.
(20 points)
5. Did every cell have a nucleus? Did each nucleus contain roughly the same material? (20 points)
Study Questions
1. Why did you specifically use the root of the onion? Does this part of the onion grow fast or slow? Why
does this matter? (10 points)
2. What do you think the structures were inside of a nucleus? (10 points)
3. Why do you think that the structures were oriented in different ways, in the different looking cells?
(10 points)
4. Where do cells come from? (10 points)
5. What do you think the function of a chromosome is? (10 points)
6. How many chromosomes exist in a normal cell? How does this compare to the cells in a newly made cell?
(10 points)
7. Does it appear that the cells reproduce in a cycle? Explain in detail. (10 points)
8. Suppose we were going to look at a bacterial cell’s nucleus. Explain what difficulties we might run in to.
(20 points)
9. Where does a bacterial cell store it’s DNA? (10 points)
10. Using the space below, draw a Eukaryotic cell and depict where DNA is stored, then draw a prokaryotic
cell and depict where DNA is stored. Use color. (100 points)
Eukaryotic
Prokaryotic