Required Practical 2 - Mitotic Index

Question 1

Where in the plants can cells 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

Prepping root tip slide method

Answer 3

1. place 2cm of root tip in hydrochloric acid for 10 mins
2. set up microscope
3. rise the root tip in distilled water on the watch glass
4. cut off 1mm of root and place it on the microscope slide
5. cover (with toluidine blue) stain and macerate
6. add the cover slip making sure that there are no bubbles

Question 4

Formula for mitotic index

Answer 4

Mitotic index = (number of cells with visible chromosomes/ number of cells in sample) x100

Question 5

What are the hazards and precautions

Answer 5

• HCL - corrosive, avoid skin contact
• Toluidine Blue O stain - irritant, avoid skin contact
• scalpel - cut away from finger

Question 6

why do you use the root tip

Answer 6

this is where cell division is occuring

Question 7

why do you add a stain

Answer 7

the highlight the DNA

Question 8

why do you need a thin layer

Answer 8

for light to get through to make observations

Question 9

common problems

Answer 9

• no fixate used so enzyme hydrolyse cells
• no stain used
• no cells dividing
• multiple layers of cells (not squashed enough)

Question 10

how to investigate herbicides

Answer 10

• use a range of at least 5 different herbicide concentration
• control all other variables eg species of plant, same distance from root tip, temperature
• plot mitotic index on graph
• minimum concentration where mitotic index is 0%