Required practical 2

Question 1

What is the method of required practical 2 (1)

Answer 1

1)Cut off 2 roots close to the garlic bulb and place them onto the white tile.
2)Add 1 cm depth of 1M hydrochloric acid to the test tube. Preheat the acid by placing the test tube in a water bath at 60 degrees
3)Using a knife cut off root tips at 0.5 cm. Keep the tips and discard the rest

Question 2

What is the method of required practical 2 (2)

Answer 2

4) Use a paintbrush to gently place the root tips in preheated acid. Return to the water bath for 5 minutes
5) Carefully pour the hot acid and root tips from the test tube into the small evaporating dish
6)Using the paintbrush transfer the root tips from the small dish into he beaker of cold water for 1 minute to wash the root tip

Question 3

Method for required practical 2 (3)

Answer 3

7) Use the paintbrush to gently hold the root tips. Rest the paint brush on some filter paper to remove as much water as possible
8) Transfer the root tips to a clean microscope slide
9)Place a second microscope slide on top of the root tips at right angles to the first and squash the root tip between the slides. Seperate the slides so you now have 2 slide for staining

Question 4

Method for required practical 2 (4)

Answer 4

10) Add one drop of acetic orcein stain to each slide and leave for 7 minutes
11) Add a cover slip to each slide lowering the cover slip with a mounted needle

Question 5

Why was a root tip used

Answer 5

This is where mitosis occurs the most

Question 6

Why was a stain used

Answer 6

To make the chromosomes visible

Question 7

Why was root tip firmly squashed

Answer 7

To ensure its one cell thick so light can pass through

Question 8

Why could a different garlic root tip affect results

Answer 8

Genetic differences
Age of root tip
Water availability
Temperature

Question 9

Suggest 2 variables that have to be controlled to ensure similar root growth

Answer 9

same water
same age
same ions

Question 10

How could the proportion of dividing cells in a thin section be determined

Answer 10

Count the total number of cells and then count the cells undergoing mitosis and divide them by eachother

Question 11

Explain the change in proportion of dividing cells with increased distance from the root tip

Answer 11

It decreases at a constant rate then goes to 0 as no cells are undergoing mitosis as cells further back are too old or become specialised

Question 12

Suggest how a root tip gets longer

Answer 12

New cells added at the tip cells increase in volume and in length as the vacuole increases due to osmossi