Practice question

Colchicine, an alkaloid from Colchicum autumnale, binds to tubulin dimers and blocks microtubule polymerization. Without functional spindle fibers, duplicated chromatids cannot migrate to poles at anaphase, and kinetochore tension fails. Cells exit mitosis with doubled chromosome number in a single restitution nucleus, creating polyploid or C-mitotic cells. In plant breeding, seedling meristems soaked in low colchicine produce tetraploids with larger organs, thicker leaves and increased vigor. Oryzalin and trifluralin act similarly. Effect is specific to spindle disruption, not direct mutagenesis or DNA breakage itself.