Investigation 5.6 – Mitosis Lab
Name: ___________________________________
Date: ___________ Period: _______ Group:_____
Introduction
A single fertilized human egg cell will divide to form two cells.
Later, these two cells will each divide into two cells. In time, millions of
cells are produced. The division of nuclear material in which each new
cell obtains the same number of chromosomes and the same nuclear
code as the original cell is called mitosis. Mitosis occurs in four phases.
There is an interphase between each mitosis.
In this investigation, you will:
- Locate cells in prepared onion root slides that are in the process
of dividing by mitosis.
- Identify cells in interphase and in each of the four stages of
mitosis in the onion root tips by comparing them with diagrams.
- Study the changes which occur in a cell as it undergoes mitosis.
Materials
Microscope
Prepared slides of onion root tip (Allium), longitudinal section
Television
Camera
Procedure
Locate with a microscope the region of rapidly dividing cells on the
prepared slide of onion root tip, the meristematic region. After locating
the cells under low power, switch to high power. Answer the following
questions about each of the phases of mitosis.
Interphase
Locate a cell in interphase. Show your teacher and get a stamp.
1. Describe the contents of the nucleus during interphase.
_____________________________________________
2. Are a nucleolus and nuclear membrane present in the cell?
______
3. Are distinct rod-shaped structures called chromosomes easily
observed in the nucleus at this time? ______
4. What term is used to describe the nuclear contents during
interphase? ___________________
5. What important event occurs to chromosomes during interphase?
__________________
6. What other event(s) occur during interphase?
___________________________________________________
___________________________________________________
Prophase
Locate a cell in prophase. Show your teacher and get a stamp.
7. Are chromosomes now visible during prophase? ________
8. Describe the changes that have occurred to the nucleolus and
nuclear membrane from interphase to prophase.
____________________________________________________
____________________________________________________
Onion Root Tip:
Metaphase
Locate a cell in metaphase. Show your teacher and get a stamp.
9. Describe where the chromosomes are now located.
____________________________________________________
10. Can evidence of chromosome duplication (replication) now be
observed? _______
11. What are the fibers called that become visible during this phase?
____________________
12. What term is used to describe the structure at which each fiber
attaches to a chromosome?
Anaphase
Locate a cell in anaphase. Show your teacher and get a stamp.
13. In metaphase, chromosomes were lined up along the cell’s center.
Describe what happens to each of the chromatids that makes up a
chromosome during anaphase.
____________________________________________________
____________________________________________________
14. Toward what area of the cell are the chromosomes being
directed? ____________________________
15. What structure is responsible for the movement of chromosomes
during this phase? _____________________________
Telophase & Cytokinesis
16. What cell parts have begun to reappear? (hint: see question #8)
_____________________________________________________
Conclusion & Analysis
The new cells produced during mitosis are called daughter cells. Find
two daughter cells that resemble the picture on the right.
17. How many cells have now formed from the original cell? _______
18. Explain how the number of chromosomes found in each daughter
cell compares to the number found in the original cell before
mitosis. (Hint: re-read the introduction)
__________________________________________________________________________________
19. What phase would the daughter cells enter after being formed? ____________________
20. The term “mitosis” comes from the Greek word meaning “thread.” Explain why this word may be helpful
in describing this process of nuclear division.
__________________________________________________________________________________
__________________________________________________________________________________
21. Animal and plant cells both undergo mitosis but with small differences.
a. Centrioles are only found in one type of cell. Which one: animal or plant? _________________
b. A cell plate forms during telophase of mitosis in plant cells. What is a cell plate? Describe.
____________________________________________________________________________
22. Explain how the process of mitosis (with interphase) helps an organism to grow in size.
__________________________________________________________________________________
__________________________________________________________________________________