Chromosome Study During Cell Division I


  • Take a large sized mature onion a week before the experiment. Cut all the dried roots from the stem at the base of the bulb. Now place these onions on the mouth of couplin jars filled with water in such a way that the stem portion must be dipped continuously in water. In about a week the new roots would develop and would start growing downward in the water.
  • Take the onions and cut the milky white portion of root tips viz., up to 5 mm length. Cut each piece into smaller pieces and fix them in Carnoy fixative for half an hour
  • Transfer the material to 90% alcohol and then to 70% alcohol keeping the material for 10 minutes in each. Now preserve the material in 70% alcohol.
  • Take few pieces from 70% alcohol in a watch glass in few drops of 1N HCI and leave for 5 minutes. This will make the material soft.
  • Drain off the HCI and wash the pieces with a little distilled water at least twice or thrice.
  • Put the root tips on a clear slide on right hand side and pour a few drops of 2% acetocarmine stain. Warm the slide gently on sprit lamp for few minutes at least 3-4 times but never let it boil. Cool and leave it for 10 minutes in the stain. Now drain the excess of stain with the help of filter paper and put few drops of 45% acetic acid.
  • Place a cover slip over the material and put above the coverslip a piece of blotting paper or filter paper folded two to three times. Press the coverslip gently with the thumb to break the cell membranes.
  • Observe the slide under the microscope first in low power and then in high power.