Practical 2 - Mitotic Index

Question 1

Describe the process of preparing stained squashes of cells from plant root tips.

Answer 1

1. HCl is added to bottle and heated in water bath that’s set at 55℃
2. add 5cm^3 of HCl to a petri dish
3. use scalple to cut 5mm of the root tip off and add it to petri dish
4. leave it there fore 15 minutes
5. remove root tips and rince with distilled water
6. dab it dry and place root tip on a slide and add acetic orcein ontop using pipette
7. place cover slip on using a mounted needle
8. gently press down the coverslip and then place the slide onto the stage to be observed by a optic microscope

Question 2

How do you calculate mitotic index?

Answer 2

1. count the amount of cells in view that are undergoing the stages of mitosis
2. then count the amount of cells in view
3. divid the cells undergoing mitosis by the amount of cells to calculate the mitotic index

Question 3

why is the root tip soaked in HCl?

Answer 3

• in order to separate the cells by hydrolysing the pectin that holds the plant cells together , which allows the stain to diffuse in
• in order to stop mitosis

Question 4

Why should the cover slip be pressed down?

Answer 4

• creates a single layer of cells
• this allows light to pass through

Question 5

Why is acetic orein used?

Answer 5

it stains the chormosomes so it can be seen more easily

Question 6

Why are the first 5mm of the root tip used?

Answer 6

it’s where the meristem is which is a tissue where mitosis occurs

Question 7

How do you ensure mitotic index is accurate?

Answer 7

examine a largev number of fields of views to ensure a representative sample

Question 8

What does the cell count tell you about each stage of mitosis?

Answer 8

It shows the relative duration of each stage of the cell cycle. The longer the stage the more cells are likely to be going through it (therefore the higher the cell count)