Name__________________________________________Period___________
Determining time spent in different phases of the cell cycle
The life cycle of the cell is typically divided into 5 major phases. The phases are listed
below, along with the major events that occur during each phase.
Interphase. The cell is engaged in metabolic activity and performing its
duty as part of a tissue. The DNA duplicates during interphase to prepare
for mitosis (the next four phases that lead up to and include nuclear
division). Chromosomes are not clearly visible in the nucleus, although a dark
spot called the nucleolus may be visible.
Prophase. Chromatin in the nucleus begins to condense and becomes visible
in the light microscope as chromosomes. The nuclear membrane dissolves.
Microtubules attach at the centromeres (at this point sometimes called
“kinetochores”) and the chromosomes begin moving.
Metaphase. Spindle fibers align the chromosomes along the middle of the
cell nucleus. This line is referred to as the metaphase plate. This
organization helps to ensure that in the next phase, when the chromosomes
are separated, each new nucleus will receive one copy of each chromosome.
Anaphase. The paired chromosomes separate at the kinetochores and move
to opposite sides of the cell. Motion results from a combination of
kinetochore movement along the spindle microtubules and through the
physical interaction of polar microtubules.
Telophase. New membranes form around the daughter nuclei while the
chromosomes disperse and are no longer visible under the light microscope.
Cytokinesis or the partitioning of the cell may also begin during this stage.
Name____________________________________________Period_________
Online Onion Root Tips
Determining time spent in different phases of the cell cycle
At your computer type in the following URL
http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html
Read through the information on the page and click next at the bottom. The next page will
summarize in pictures and text the five major phases of the cell cycle. You have a copy to
refer to for the rest of the activity. After reviewing each phase and its major events,
click next at the bottom to continue with the activity.
The assignment:
In this activity, you will be presented with cells from the tip of an onion root. You will
classify each cell based on what phase it is in. At the end you will count up the cells found in
each phase and use those numbers to predict how much time a dividing cell spends in each
phase. You can base your calculation on a total cell cycle of 24 hours.
Enter data in the table below as you go along or at the end of the activity.
Interphase
Number of
cells
% of time in
phase
# cells
total
Metaphase
Anaphase
Telophase
TOTALS
36
100%
X 100
Time spent in
phase in 24
hr. per.
% X 24
Prophase
24 hrs
Conclusion questions (answer in complete sentences)
1. Of the four stages of mitosis, which one takes the most time to complete?
2. Which is the shortest stage in duration?
3. What would happen if the process of mitosis skipped metaphase? telophase?
4. Identify the phases of mitosis shown in the pictures below.
4.On the back of this page, create a BAR GRAPH comparing the percentages of time
the cells are in each phase. Be sure to label the graph properly (both the X and the Y
axis) and to give the graph a title. Remember all labels and titles must be underlined in
a graph. (Use a straight edge for neatness!)