Mitosis core practical

Question 1

what is the method and purpose of steps

Answer 1

1. cut off 5mm of onion root tip
2. place root tips in acid (HCl) and let soak for 5 minutes to soften the material and break the middle lamella
3. place root tips in water for 5 minutes to wash off the HCl
4. transfer to a microscope slide to prepare for viewing
5. macerate with a mounted needle on microscope slide which separates cells to help obtain a singe layer of cells
6. stain with toluidine blue because it binds to DNA so the chromosomes appear blue under the microscope (makes then more visible)
7. place cover slip on the slide and gently squash in order to obtain a single layer of cells
   8 observe cells under microscope at 400x magnification (red lense) so chromosomes can be seen

Question 2

what are the risks and the safety precautions that need to be taken

Answer 2

risk of cuts when using sharp scalpel to cut root tip - cut away from you
skin/eye damage from hydrochloric acid and toluidine blue stain - wear lab coat, safety goggles and gloves
coverslip can break when squashing cutting skin - press down on coverslip with paper towels

Question 3

how to calculate the mitotic index

Answer 3

number of cells with visible chromosomes/total number of cells in the field of view