required practical 2:preparation of stained squashes of cells

Question 1

why is toluidine blue used?

Answer 1

chromosomes are stained and so are visible as you couldn’t see them if not

Question 2

why is the tissue macerated?

Answer 2

to separate the cells

Question 3

why is the tissue ‘squashed’ under a cover slip?

Answer 3

to form a single layer of cells so light can pass through

Question 4

why should the student take care not to squash the cells sideways?

Answer 4

to avoid damage to the cells

Question 5

why are cells from the root tip used?

Answer 5

these are undergoing mitosis as plants grow at the root/shoot tips

Question 6

why calculate the % of cells undergoing mitosis, rather than counting the number of cells?

Answer 6

different tissues may have different number of cells so the results are more comparable calculating the % of cells

Question 7

why would someone choose a large sample of cells e.g. 200 cells?

Answer 7

for a representative sample

Question 8

why may results vary if comparing to a different tip of the same species?

Answer 8

• different temperature

- different type of root tip e.g. garlic

Question 9

what should the student have done when counting cells to ensure that the mitotic index obtained for the root tip was accurate?

Answer 9

• count repeatedly

- examine a large number of fields of view/cells

Question 10

how can a chemical stop the growth of roots?

Answer 10

• stops anaphase i.e. chromatids moving to opposite poles of the cell
• stops division via cytokinesis
• disrupts spindle fibres forming