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BACKGROUND
A normal cell cycle occurs because of cell cycle and the primary function of cell cycle is duplicating the chromosomal DNA, which further divides into two identical daughter cells. In this process there are four main phase G1 phase, S phase, G2 phase and M phase. Among these two vital phases are S phase where DNA replication occurs and M phase where mitosis occurs. In mitosis again, there are several phases like prophase, metaphase, anaphase and telophase. Cell cycle regulation is very important without which detection or repairing of genes is difficult and which can cause uncontrollable division of cell leading to cancer. There are certain alkaloid drugs that can inhibit the uncontrolled growth or division of cells. Colchicine is such drug that has been isolated from plant called colchicum autumnale and this drug at present is used for treating various diseases like gout, Bechet’s disease and is under investigation as an anti-cancer drug. It posses the capability of inhibiting the microtubule polymerization by getting binded to protein tubulin thereby leading to microtubule degradation. This in turn causes disruption of mitosis and causes cell death as microtubules makes mitotic spindles. Without presence of microtubule the cell cannot divide. This can prove to be very much beneficial for treating cancer. The basic objective of this experiment is to study polyploidy in Onion root tip by colchicine treatment.
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REQUIREMENTS
Sample: Rooted bulbs of onion
Chemicals: 1% aqueous solution of colchicine
Acetocarmine
45% acetic acid
Others: Small beakers
Water
Coverslips
Slides
Burner
Microscope
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PROCEDURE
In a small beaker fill water and in it keep the rooted bulb of onion in such a way that the roots hang in water. Then in another small beaker fill 1% aqueous solution of colchicine and similarly place the rooted bulb of onion.1 The allow the roots to grow. Now keep the root tips in two separate slides and make the squash by following acetocarmine technique. And observe under microscope.
Acetocarmine technique
Cut the distal end of the root tips in 45% acetic acid and the stain it in acetocarmine and put in it a cover slip. The squash it a little by heating and pressing.2 After that study various stages of mitosis.
It will be observed that there are normal stages of mitosis in water treated root tips and in the other hand the colchicine treated root tips will show many abnormalities like separation of daughter chromosome to their poles due to colchicine and treatment with colchicine also shows doubling of chromosome in the nucleus that induces polyploidy.3
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CONCLUSION
The alkaloid obtained from certain species of colchicium causes doubling of chromosomes thereby inducing polyploidy.
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REFERENCES
- Brown, nellie a. Colchicine in the prevention, inhibition, and death of plant tumors. Phytopathology, 29: 221-231. 1939
- Clearkin, p. A. The effect of colchicine on normal and neoplastic tissues in mice. J. Path. & bact., 44:469- 480. 1937
- Poulssox, k. T. Colchicin behandling av maligne svulster hos mus. Norsk. Mag. F. Laegevidensk., 96:735-736. 1935.
