Unit 3: Mitosis and Meiosis
Internet Activity
ONION ROOT TIPS AND THE CELL CYCLE
Actively dividing cells pass through a predictable series of stages called the cell cycle. A cell
cycle starts with interphase, just after a new cell is formed by mitosis. During interphase, the cell
duplicates its DNA and increases its mass and number of cytoplasmic components. This prepares
the cell for the next round of mitosis. The cell cycle ends when the cell divides. If you look under
a microscope at cells from actively dividing tissue, you will find that their cell cycles are not
synchronized. Some cells are in interphase, while others are in the various stages of mitosis. By
noting the number of cells in each stage, it is possible to calculate the relative lengths of each
phase of the cell cycle.
Activity
In this activity, you will calculate the lengths of the various phases of the cell cycle in an onion
root tip. First you will view some slides and graphics of onion root tips provided by the
Molecular Expressions Photo Gallery. Then you will complete the online activity provided by
the Biology Project at the University of Arizona. Once you have completed this exercise, you
will play the Cell Cycle game.
PART 1
Use your browser to go to Molecular Expressions Photo Gallery: Mitosis
http://www.microscopy.fsu.edu/micro/gallery/mitosis/mitosis.html.
Notice in the micrograph at the top of the page that there are cells in a variety of stages. View the
onion slides in this section. Once you have read this entire page, click on "mitosis" in the
sentence "Learn the steps in mitosis ...” This will take you to a Java tutorial. Keep in mind what
you have learned here as you proceed to the second part of the activity.
PART 2
Use your browser to go to Online Onion Root Tips at
http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html.
Begin by reading the description of the five major cell phases. You will need to keep this
information in mind during the activity. Keep your own copy of your data using the data table
provided. You will need it to answer the questions.
Proceed through the activity, identifying the phase for each cell you are shown. Pay attention to
the hints if you misidentify a cell at first.
PART 3:
When you have completed the worksheet, including the drawings and the questions, go to the
following website and work through the Cell Cycle game.
http://nobelprize.org/educational_games/medicine/2001/cellcycle.html
You are on your honor to try your best to complete the game.
Unit 3: Mitosis and Meiosis
Name: _________________
Internet Activity ONION ROOT TIPS AND THE CELL CYCLE
After you have correctly identified the phases, sketch a picture of the cells going through
each phase. You must include at least 4 different chromosomes in the nucleus in your sketches:
Interphase:
Prophase:
Metaphase:
Anaphase:
Telophase:
Data Table: Cell Cycle
Interphase
Prophase
Metaphase
Anaphase
Telophase
Total
number of cells
36
percent of cells
100%
When you have completed the activity, answer the following questions:
1. What percent of cells were in interphase?
2. What percent were in mitosis?
3. Which phase of mitosis takes the longest?
4. During which stage is the nucleolus visible as a dark spot?
5. How can you recognize a cell in metaphase?