Name:____________________________________
Observing Mitosis
Background Information:
Growth in an organism is carefully controlled by regulating the cell cycle. In plants, the roots continue to grow as they search for
water and nutrients. These regions of growth are good for studying the cell cycle because at any given time, you can find cells that are
undergoing mitosis.
In order to examine cells in the tip of an onion root, a thin slice of the root is placed onto a microscope slide and stained so the
chromosomes will be visible. Although slicing the onion root captures many cells in different phases of the cell cycle, keep in mind
that the cell cycle is a continuous process. Scientists have divided the process into 5 phases, each characterized by important events,
but these divisions are still arbitrary.
Pre-Lab (Online)
Go to the following website http://biology.about.com/od/mitosis/ss/mitosisstep.htm#step1 DRAW, LABEL, and DESCRIBE a cell
in each phase of the Cell Cycle as shown in the pictures.
Take the Quiz at the end of the website. Write your score out of ten HERE _________________
Go to google.com and type in Bio Rutgers Mitosis lab, click on Mitosis lab. Click on Begin assignment. Practice determining
cell phase in the onion root tip. Click on Part 4, Mitosis in an Animal Cell. Practice determining cell phase in animal cells.
Write a summary describing the difference between Mitosis in Plant cells and Mitosis in animal cells.
In the space below; make a hypothesis as to which phase cells spend most of the time in and why. REMEMBER
If….then….because
Go to http://www.biology.arizona.edu/cell_bio/activities/cell_cycle/cell_cycle.html
Copy the table here and fill it out. Don’t forget an appropriate title for your table.
Lab Instructions:
With your partner you will use the microscope to observe mitosis in prepared slides of plant and animal cells. Each time you find a
cell in the phase of mitosis you are looking for, draw a detailed drawing of that cell (for this lab you do not need to draw the entire
field of view) on your data sheet. You will have two sets of drawings; one for onion and one for whitefish. Make sure to follow the
information from your microscope drawings guideline sheet for full credit on your drawings or if you need help focusing.
Helpful Hints:
When looking at the onion root, look toward the tip, but not at the very tip of the root on your prepared slide, this is where you will
find the greatest variety of cells at various stages because this is where mitosis is happening the most!
Challenge – If time. Very similar to above computer activity.
Focus on a magnification of 100x. Count how many cells are in each phase. Repeat and create a data table for 3 fields of view on the
stages of mitosis. Calculate the percent of time spent on each phase based on the average number of cells in that phase.