Final answer:
Chemotherapy drugs like vincristine and colchicine disrupt mitosis by inhibiting microtubule assembly, while paclitaxel prevents microtubule disassembly. These drugs target spindle fibers, which are essential for chromosome segregation during cell division, ultimately arresting the cell cycle at specific phases.
Step-by-step explanation:
Chemotherapy drugs such as vincristine, colchicine, and vinblastine decrease microtubule assembly by binding to tubulin. Other drugs like paclitaxel (Taxol) inhibit microtubule disassembly, leading to the formation of abnormal bundles of microtubules. These drugs target the spindles which are crucial for the proper segregation of chromosomes during cell division.
Vincristine and colchicine prevent the formation of spindles by inhibiting the polymerization of tubulin into microtubules, which disrupts the mitotic phase in cell division, leading to cell cycle arrest in metaphase. On the contrary, paclitaxel stabilizes the microtubules and prevents their depolymerization, which also interferes with chromosome segregation, particularly during mitotic anaphase and telophase.