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
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.
Interphase / Prophase / Metaphase / Anaphase / Telophase / TOTALSNumber of
cells / 36
% of time in phase
# cells X 100
total /
100%
Time spent in phase in 24 hr. per.
% X 24 / 24 hrs
Enter data in the table below as you go along or at the end of the activity.
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 GRAPHcomparing 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!)