Mitosis

Question 1

Culture medium and its colour and where are the cells growing?

Answer 1

• In this practical the cells are growing on the surface of coverslips placed in a Petri dish.
• The coverslips can be easily removed, stained and mounted on slides for microscopic examination.
• The culture medium is a complicated mixture of salts, nutrients, vitamins and other factors which promote growth and cell division.
• The pink colour is due to a pH indicator – it will go orange then clear if the medium is too acid, or
  puce then purple if too alkaline.

Question 2

What is the aim of the experiment and what inhibitor is being used?

Answer 2

• Experiment involves comparing uninhibited cells with cells which have spent an hour in culture medium which is identical except for the addition of an inhibitor
• Inhibitor of cell division: VINBLASTINE
• Used as part of chemotherapy treatment of certain cancers; dose carefully regulated so that it affects the most rapidly dividing cells, i.e. tumour cells

Question 3

Staining process

Answer 3

• Clean the forceps
• Take a coverslip with forceps
• Briefly wash in phosphate-buffered saline (PBS)
• Fix the cells in acid-alcohol (15 secs)
• Rinse in distilled water
• Stain chromosomes: one drop of neutral red stain
• Lower a slide onto it
• Remove excess stain with tissue
• Examine under microscope

Question 4

Why is it important to not let the cells dry out?

Answer 4

• The cells will die if deprived of their growth

medium.

Question 5

How should the cell be placed into the vinblastine solution?

Answer 5

• Remove one of the coverslips from the Petri dish and transfer it to a slot in the Columbia jar, which contains a solution of vinblastine in culture medium.
• Pick up the coverslip using the forceps provided, making sure you know which side of the cover slip has the cells on it
• Make sure that you pick up the coverslip close to the
  edge
• Place the coverslip in the Columbia jar so that the side with the cells faces the spot marked on one side of the jar.
• Leave for an hour

Question 6

What does vinblastine do?

Answer 6

it disrupts the formation of the mitotic spindle

Question 7

Which animal did the cells come from and why?

Answer 7

The cells used in this practical derive from the frog Xenopus

• They were chosen mainly because cells from a cold-blooded animal will continue to grow and divide actively at room temperature in the practical laboratory whereas mammalian cells would need to be maintained at 37.C in special incubators.
• They are also free from the potential health hazards associated with human cell lines which can carry viruses infectious to people.