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Q.
Colchicine prevents the mitosis of cells at which of the following stage?
CMC MedicalCMC Medical 2008
Solution:
If a cell is treated with certain drugs such as colchicine, vihcristine the assembly of the microtubules is inhibited, while the disassembly continues leading to disorganization of microtubules. The assembly of microtubules cause spindle apparatus formation during metaphase. Therefore, the cell division prevented at metaphase (movement of chromosomes also). Interphase is divided in $ {{G}_{1}},\,S $ and $ {{G}_{2}} $ -phase. These are characterized by synthesis of RNA, synthesis of DNA and tubulin and protein synthesis respectively. During prophase the chromosomes are thin thread-like and condensed. During anaphase the chromosomes move towards opposite poles. When treated with colchicine the cell cycle arrests at metaphase and not go to anaphase.