Squash preperation of Onion root tip for mitosis.pdf

## Squash Preparation of Onion Root Tip for Mitosis and Calculation of Mitotic Index

**Materials:**

* Onion bulb
* Petri dish
* Water
* Forceps
* Scalpel
* Acetocarmine or aceto-orcein stain
* Microscope slides
* Coverslips
* N/10 HCl (hydrochloric acid)
* Blotting paper

**Procedure:**

1. **Root Tip Growth:**
* Place an onion bulb in a petri dish containing water.
* Ensure the base of the bulb is submerged in water.
* Allow the roots to grow for 3-5 days.

2. **Root Tip Collection:**
* Carefully remove the onion bulb from the water.
* Cut 1-2 cm of the actively growing root tips.
* Place the root tips in a watch glass.

3. **Fixation:**
* Add a few drops of acetocarmine or aceto-orcein stain to the watch glass.
* Allow the root tips to soak in the stain for 5-10 minutes.
* Rinse the root tips in water to remove excess stain.

4. **Squash Preparation:**
* Place a root tip on a microscope slide.
* Add a drop of N/10 HCl to soften the tissues.
* After 5-10 minutes, blot the excess acid with blotting paper.
* Add a drop of acetocarmine or aceto-orcein stain.
* Place a coverslip on top of the root tip and gently squash it using the blunt end of a pencil.

5. **Microscopic Observation:**
* Examine the slide under a microscope using a high-power objective.
* Identify cells in different stages of mitosis: interphase, prophase, metaphase, anaphase, and telophase.

6. **Mitotic Index Calculation:**
* Count the total number of cells observed.
* Count the number of cells in mitosis.
* Calculate the mitotic index using the formula:
```
Mitotic index = (Number of cells in mitosis) / (Total number of cells)
```

**Diagram:**


**Note:**

* Ensure the root tips are fresh and actively dividing for optimal results.
* Avoid excessive squashing, as this can damage the cells and chromosomes.
* Use a high-quality microscope with a good objective lens for clear visualization of mitotic stages.
* Repeat the experiment multiple times to obtain reliable results.

Image citations: [[1]](https://www.notesonzoology.com/practical-zoology/top-3-experiments-to-demonstrate-mitosis-and-meiosis-in-animals/3001)

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