RP2: Preparation of a root tip & Calculation of mitotic index

Question 1

Where does mitosis take place in plants

Answer 1

in the root tip/meristem

Question 2

Describe the process of mounting

Answer 2

Place a cover slip on the slide
squash the preparation by pressing between layers of filter paper
Examine the preparation on the microscope using suits bull magnification

Question 3

How do you calculate/what is the formula for the mitotic index

Answer 3

number of cells in mitosis / total number of cells

cells in interphase do not count

Question 4

Which stage is the shortest and how is this evident from the preparation

Answer 4

Prophase as that all the least number of cells with the stage of prophase

Question 5

what is maceration And why is it important

Answer 5

macerating fluid breaks down the biological glue, which holds tissue together. Using macerating fluid helps is to visualize the individual cells in the tissue, therefore the different stages in mitosis

Question 6

Why is the stain added to the preparation

Answer 6

The stain is added so when we look at the cells through a microscope we can see the /contrast of density in an individual cell. It stains the DNA strongly

Question 7

Why is squashing the preparation after staining important

Answer 7

so we could get a single layer of cells and we can see them clearly. So cells don’t clump together and overlap

Question 8

Why must do not push the coverslip sideways when preparing slide

Answer 8

so the cells don’t split open, we might damage the cells and we could damage the chromosomes

Question 9

How could you make the mitotic index that you calculated more reliable

Answer 9

you could take a bigger sample
You could take the mean or the average of multiple mitotic index’s
you could repeat it and choose different fields of view

to increase reliability do the experiment more than once

Question 10

what is the evidence that a cell is an anaphase

Answer 10

The spindle fibres have contracted and the centromere has split. The pairs of sister chromatids are separated and are dragged to the opposite ends of the cells poles

Question 11

Why do we use a mounted needle

Answer 11

to lower down the cover slip and make sure you don’t get any air bubbles

Question 12

Why do we use stain

Answer 12

to stain in the nucleus. Staining the chromosomes means that we can visualise what stage in mitosis a cell is in

Question 13

Why do we use a scalpel

Answer 13

to make sure we get a very thin slice of the specimen

Question 14

Why does the sample have to be thin

Answer 14

So that light can pass through and create an image. So cells don’t overlap and we get a single layer

Question 15

Why do we take a sample from the root tip

Answer 15

Because this is where mitosis occurs

Question 16

Why do you apply pressure firmly to the cover slip but not slide the coverslip

Answer 16

To make sure we get one layer of cells/a single layer of cells to ensure light can pass through and an image can be created

Sliding the coverslip could make the cells clump together. You could also damaged the cells therefore damaging the chromosomes

Question 17

How could you standardise the method when calculating the mitotic index

Answer 17

in a certain field of view you would have cells that half fit into the field of view. You should only count the cells that fit fully into the field of view