Mitosis in Onion Cells
Mitosis
is part of the cell cycle when replicated chromosomes are separated
into two new nuclei.
Observation Steps
1.
With an adult’s supervision, cut a small piece of an onion (approximately
¼ - ½ inch).
2.
Using the forceps, peel off the membrane from the underside (the rough
side).
3.
Place the membrane flat on the surface of a microscope slide.
4.
Add 1-2 drops of the non-toxic stain. Please wait for 2 to 3 minutes for the
onion to absorb the stain.
Caution:
Protect surfaces & clothing when
using stain!
5.
Using the plastic transfer pipet rinse the excess stain with water.
6.
Add one cover glass on top of the onion membrane. Make sure there are
no air bubbles underneath.
7.
Begin with the stage platform at its lowest position. Rotate the nosepiece
to ensure 4X objective lens is being used. Turn on the bottom illuminator
to shine the light up through the stage.
8.
Place the onion cell slide onto the stage of the microscope.
9.
Looking through the eyepiece, SLOWLY turn the focusing knob to allow
the 4X objective to get closer to the slide until an image comes into focus.
10.
Increase the magnification and repeat the process above; please allow
enough space between objectives and specimen for proper viewing.
In the picture below, the dark blue images are the chromosomes of the onion
membrane. In some cells you can see the chromosomes being pulled apart to
create the new cells.
