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An alkaloid drug, extracted from the autumn crocus (Colchicum autumnale), that reacts reversibly with the protein tubulin and prevents its polymerization into microtubules. Consequently microtubule-assisted processes, such as the movement of organelles, are inhibited. Colchicine is often applied to dividing cells when making a chromosome preparation. It inhibits spindle formation and thus the condensed chromosomes are scattered rather than aligned on the spindle. This greatly facilitates their examination. If colchicine is applied to cells undergoing meiosis then the failure of the homologous chromosomes to separate results in the formation of diploid gametes. Colchicine is thus an important tool for the artificial induction of polyploidy and in other experimental studies, such as investigations of pollen development. It may also be used to render sterile hybrids fertile by doubling their chromosome number so the chromosomes have a homologue to pair with at meiosis.
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