required practical 2: calculating mitotic index using plant cells

Question 1

how do you prepare a sample of cells for a microscope

Answer 1

cut a thin slice of the root tip and place on slide
soak in HCl
stain
add coverslip
squash

Question 2

why are root tips used

Answer 2

this is where dividing cells are found - where mitosis occurs

Question 3

why is a stain used

Answer 3

to distinguish chromosomes, making them visible

Question 4

why do you sqaush the cover slip

Answer 4

to create a single layer of cells, to allow light to pass through the chromosomes

Question 5

why are the cells soaked in acid

Answer 5

to separate the cells, allows stain to diffuse into the cells, stops mitosis

Question 6

how do you set up and use an optical microscope

Answer 6

clip slide onto stage and turn on light
select lowest power lens
use coarse and fine focusing dial to get a clear image

Question 7

what is the mitotic index, how do you work it out?

Answer 7

it is the proportion of cells undergoing mitosis, with visible chromosomes
number of cells undergoing mitosis/total number of cells

Question 8

how do you calculate the time cells are in a certain phase of mitosis

Answer 8

identify proportion of cells in named phase = number of cells in that phase/ total number of cells * length of cell cycle