Stages of mitosis

Question 1

Where in plant cells can undergoing mitosis be found?

Answer 1

Meristem tissue at shoot and root tips

Question 2

What is the mitotic index?

Answer 2

The ratio of cells undergoing mitosis to the total number of cells in a sample.

Question 3

Outline the procedure to prepare a root tip slide.

Answer 3

1. Warm 1M HCI to 60°C in a water bath.
2. Cut a root tip using a scalpel and add it to the HCI. Leave for 5 minutes.
3. Remove the HCI and wash with cold distilled water.
4. Dry and place on a slide. Macerate with a needle to spread out the cells.
5. Add a few drops of stain to make the chromosomes visible.

Question 4

State the formula for the mitotic index

Answer 4

Cells in mitosis / total number of cells

Question 5

State the hazards and precautions for reagents used in this procedure.

Answer 5

HCI - corrosive, avoid contact with skin and wear eye protection.
Toluidine Blue O stain - irritant, avoid contact with skin and wear eye protection.
Scalpel - cut away from fingers.

Question 6

Why is the root tip placed in hot HCI?

Answer 6

Because HCI dissolves the middle lamellae to break the cellulose cell wall. This allows the stain to permeate and the tip to be squashed more easily.

Question 7

Why is the root tip squashed/pressed down before viewing?

Answer 7

To spread out the cells in a thinner layer, so there is less overlap and more light can pass through. This makes the image clearer.