Study on effect of Colchicine on Mitotic cell division in onion root tip cells

Materials supplied
Actively growing root tips still with germinating bulb were treated in 0.05% colchicine solution for 5 hours.
Then the bulbs were left in water few 24 hours. After that the root tips were cut and fixed in Acetic Alcohol (1:3). Such fixed root tips were supplied in the class.
Staining and slide preparation were done as usual.
The slides were observed under the microscope. The following conditions abnormal were observed, besides the normal mitotic phases.

Abnormal conditions:
• Late prophase with tetraploid chromosomes.
• Much bigger and wider metaphase plate, indicating tetraploid condition.
• Much bigger daughter chromosome groups in anaphase.
• Occurrence of micronucleus/micronuclei, along with bigger daughter nucleus.

From the above noted observations, it was evident that colchicine treated resulted these conditions.

Late prophase with tetraploid chromosome

 Metaphase at tetraploid condition (Metaphase arrest)  

Characteristics i)

Two separate anaphase group

Micronucleus in daughter cell

Study 8 Checklist Remarks

  1. Laboratory rules (lab coats, instruments etc.)
  2. Can count cells at different dividing stage
  3. Can calculate cell doubling time
  4. Can identify the stages with abnormal chromosomal arrangements due to the effect of Colchicine
  5. Clean up bench and wash hands

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