Biology practical = Mitosis root tip squash

Question 1

Step 1

Answer 1

Grow garlic over a beaker of water to grow new roots
And use a scalpel to cut a few mm off the end

Question 2

How do we differentiate the cut end from the grown end (where the cells dividing)?

Answer 2

Use mounted needle to split the root at the cut end to show we cut here and so want to observe the other end

Question 3

Step 2

Answer 3

Add the tip to a tube with HCl in a water bath and leave for a few mins

Question 4

Why is HCl added?

Answer 4

To soften and loosen root tissue so cells can be separated

Question 5

Step 3

Answer 5

Place the root tip on a watch glass after separating it from HCl and rinse with distilled water

Question 6

Step 4

Answer 6

Place tip on a slide and soak up excess water with filter paper

Question 7

Step 5

Answer 7

Add 2 drops of methyl blue indicator and use blunt side of mounted needle to squish root tip

Question 8

Why is an indicator used?

Answer 8

To turn the CHROMOSOMES a colour which is visible under the light microscope

Question 9

Why do we squash the root tip?

Answer 9

So a single layer of cells can be obtained

Question 10

Step 6

Answer 10

Use mounted needle to lower coverslip at an angle to remove any air bubbles

Question 11

What is the mitotic index?

Answer 11

Counting the proportion of cells down a field of view are in mitosis

Question 12

How to find mitotic index

Answer 12

Number of cells in mitosis
——————————————
Total number of cells in field of view
X100

Question 13

How to ensure mitotic index is accurate

Answer 13

Calculate the mitotic index for a large number of field of views and find the average value