2: Using light microscope to measure mitotic index using plant cells

Question 1

How do you calibrate the eye piece graticule?

Answer 1

Count the number of epu that fit into a known length on the stage micrometer.

e.g. if 100 micrometer = 4 epu,
then 1 epu = 100/4 = 25 micrometer

CALIBRATE FOR EACH MAGNIFICATION!

Question 2

What stain is added to the transverse cut sections?

Answer 2

Toluidine blue O stain

This is a metachromatic stain.

Question 3

How do you explain low powered drawings?

Answer 3

Give a simple outline by stating the tissues within your scope.

Question 4

How do you explain high powered drawings?

Answer 4

Label CELLS within your scope

(max 10 cells)

Question 5

Where in plants can cells undergoing mitosis be found?

Answer 5

Meristem tissue at shoot and root tips.

Question 6

What is the mitotic index?

Answer 6

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

Question 7

Outline the procedure to prepare a root tip slide.

Answer 7

1. Warm 1M HCl to 60°C in a water bath.
2. Cut a root tip using a scalpel and add to the HCl. Leave
   for 5 minutes.
3. Remove from HCl and wash with distilled water.
4. Cut the tip of the root tip sample and place on a slide.
5. Add a few drops of stain to make chromosomes visible.
   https://bit.ly/pmt-edu

Question 8

State the formula for the mitotic index.

Answer 8

Mitotic index =
Number of cells with visible chromosomes /
Number of cells in sample

Question 9

State the hazards and precautions for reagents used in this procedure

Answer 9

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