Cell Cycle - Pratical 3

Question 1

what happens in G0

Answer 1

non dividing

• full differenitated
• quiescent stem cells

Question 2

How many chromosomes does the onion cell contain

Answer 2

8 chromosomes

Question 3

what is the procedure for preparing root tip squashes

Answer 3

Cut approximately 1-2 cm of the root tip off and transfer them to a test-tube containing 1M HCL.
Incubate at 60°C for 8 minutes
After which remove the tips from the HCL and transfer to a petridish containing distilled water
Leave for 3-4 minutes
Transfer the root tips to a microscope slide
Cut about 2 mm from growing tip to use (this will contain the area of cell division in which mitosis occurs) and discard rest
Add a drop of Toludene Blue to root tip
Leave to stain for 2 minutes.
Cover the root tip with a cover slip, and then carefully push down on the cover slide with the wooden end of a dissecting probe.
Push hard, but do not twist or push the cover slide sideways.
The root tip should spread out to a diameter about 0.5 – 1 cm.
scan the microscope under the 10x objective, look for the region that has nuclei relative to the size of the cell, among these cells will be ones expressing mitosis
find the cells at X40

Question 4

length of each stage of mitosis

Answer 4

Prophase (longest, approx. 2/3 of the time to complete mitosis is taken up by prophase), whereas the other stages occur in a much shorter time.

• anaphase
• telophase
• metaphase
• prophase

this is from shortest to longest