CELLS: Investigating Mitosis

Question 1

Describe how root tips can be used to investigate mitosis:

Answer 1

1. Cut 1 cm from tip of growing root - where mitosis takes place
2. Prepare boiling tube - 1M hydrochloric acid
3. Put in water bath at 60^oC
4. Transfer root tip into boiling tube + incubate for 5 minutes
5. Use pipette to rinse root tip with cold water
6. Leave to dry
7. Place on microscope slide + cut 2mm from tip
8. Use mounted needle to break tip open + spread cells.
9. Add stains
10. Place cover slop + push firmly

Question 2

Describe how to use an optical microscope:

Answer 2

1. Clip slide onto stage
2. Select lowest-powered objective lens
3. Use coarse adjustment knob to move stage up
4. Use coarse adjustment knob to move stage downwards until image is roughly focused.
5. Adjust focus with fine adjustment knob
6. If greater magnification needed = higher-powered objective lens

Question 3

How do you calculate mitotic index?

Answer 3

= number of cells with visible chromosomes / total number of observed cells