Mrs. Keadle JH Science
1
Onion Cell Mitosis
Name__________________________________ period _____
date assigned_____________ date due ______________ date returned _____________
Onion Cell Mitosis
Background:
In a growing plant root, the cells at the tip of the root are constantly dividing to allow the
root to grow. Because each cell divides independently of the others, a root tip contains cells
at different stages of the cell cycle. This makes a root tip an excellent tissue to study the
stages of cell division.
Materials:
microscope prepared slides of onion (allium) root tips
Procedure:
1. Obtain a prepared slide of an onion root tip (there will be three root tips on a slide). Hold
the slide up to the light to see the pointed ends of the root sections. This is the root tip where
the cells were actively dividing. (The root tips were freshly sliced into thin sections, then
preserved when the slide was prepared.)
2. Place the slide on the microscope stage with the root tips pointing away from you. Using
the focus adjustment, obtain the clearest image possible on the laptop. Just above the root
“cap” is a region that contains many new small cells. The larger cells of this region were in the
process of dividing when the slide was made. These are the cells that you will be observing.
3. Observe the box-like cells that are arranged in rows. The chromosomes of the cells have
been stained to make them easily visible. Select one cell whose chromosomes are clearly
visible.
4. Sketch the cell that you selected in the box on the right.
5. Look around at the cells again. Select four other cells whose
internal appearances are different from each other and the first
one that you sketched. Sketch them in the boxes below.
