Topic 2--- A: Cell Structure and Division- 5. Investigating Mitosis

Question 1

Preparing a root tip cell squash

Answer 1

• Add some 1 M hydrochloric acid to a boiling tube (should be enough to cover the root tip).
• Put the tube into a water bath that has been allowed to reach 60 degrees.
• Use a scalpel to cut 1cm from the tip from a growing root as that’s where growth occurs and transfer it into the boiling tube
• Incubate it for 5 minutes
• Use tweezers to remove the root tip from the tube and use a pipette to rinse it with cold water
• leave the tip to dry on a paper towel
• Place the root tip on a microscope slide and cut 2mm from the very tip of it
• Use a mounted needle to break the tip open and spread the cells out thinly
• Add a few drops of a stain and leave it for a few minutes (makes the chromosomes easier to see).
• Place a cover slip over the cells and put a piece of folded filter paper on top
• ## Push down firmly to squash the tissue (allows light to pass through it)

Question 2

Mitotic index calculation

Answer 2

Mitotic index= Number of cells with visible chromosomes
——————————Total number of cells obeserved

Question 3

Mitotic index

Answer 3

-Its the proportion of cells in a tissue sample that are undergoing mitosis.
-It lets you work out how quickly the tissue is growing and if theres naything weird going on