Investigating mitosis in allium root tip squash
Class practical
In the 1st week of February, Grade 11 complete the unit 3 with observing the Mitosis process in onion root tip. All students prepare their own root tip for around 4 days. They did extract the cell using Ethanoic alcohol and HCl; staining using orcenic stain, and observed under the microscope.
(Methods after some modifications)
Preparation
- Cut off 2 of the root tips with 1-2 cm length. Put the root on a watchglass and add a small volume of ethanoic acid until it cover the whole part of the root. Leave it for 10 minutes.
- Meanwhile, heat 10-25 cm3 of 1 M hydrochloric acid to 60 °C in a water bath. Students make their own water bath with beaker glass 500 ml and put the 100 ml beaker glass containing HCl inside it.
- From step 1, put the root tips on a 30 ml of tap water (in a 100 ml beaker glass) for 4-5 minutes and dry on filter paper.
- Use a mounted needle to transfer the root tips to the hot hydrochloric acid (in step 2) and leave for 5 minutes.
- Put the root tips on a 30 ml of tap water again in cold water for 4-5 minutes and dry on filter paper.
- Use the mounted needle to remove the root tips onto a clean microscope slide.
- Cut each about 2 mm from the growing root tip. Discard the rest, but keep the 2 mm tips.
- Add 1-2 drops of stain and leave for 2 minutes.
- Break up the tissue with a mounted needle.
- Cover with a coverslip and squash (tap the coverslip about 20 times by dropping a wooden mounted needle or a pencil, blunt end down, from a height of about 5 cm onto the middle of the coverslip)
- View the root tips under a microscope (x400 magnification) and look for the chromosomes within cells which are actively dividing.
- If cells are overlapping, squash the slide again. Avoid moving the cover slip from side to side.
- Make sketches of (or take photographs of) cells that show any of the stages of mitosis.
Here are the result of students work.
Hands On activity for the better understanding
-Andhyni Tombe-
AS Biology Teacher