Principles of Genetics and Breeding

Procedure and Note

1. Grow onion in mud pot or in test tubes.

2. Collect the growing root tips and wash them thoroughly to free sand particles. With a sharp blade cut the root tips of 1-2 mm length.

3. Keep the root tips for 30 min in the pretreatment chemical para dichlorobenzene.

4. Fix the root tips in fixative (Ethanol 3: Glacial acetic acid 1) for 3-6 hrs.

5. Treat the root tips in 1 N. HCl for about 15-30 min at 58-62°C for softening.

6. Take the root tips in a slide and cut into two halves longitudinally.

7. Place a cover slip over the root tip.

8. Stain the slides in 2% aceto-carmine or aceto-orcein stain.

9. Heat the slide gently over a non-luminous flame and squash the slide.

10. Observe the slides under a microscope and look for various stages of mitotic division.

Note:

i.) The root tips can be transferred to 70% alcohol for later examination.

ii.) Both staining and hydrolysis can be done simultaneously by warming the root tip in a mixture of solution containing 9 parts of 2% aceto-carmin and 1 part of 1N.HCl.