Final answer:
Microtubules rapidly assemble and disassemble, a process called dynamic instability, essential for their role in cell shape maintenance, transport, and chromosome segregation. Chemotherapy drugs like vincristine and colchicine target microtubules to disrupt cell division, useful for cancer treatment. Instability is controlled by cell cycle regulatory molecules and can be affected by certain drugs.
Step-by-step explanation:
Microtubules are part of the cell's cytoskeleton and are composed of polymerized dimers of α-tubulin and β-tubulin, forming hollow tubes with a diameter of about 25 nm. They have the dynamic ability to rapidly assemble and disassemble, making them essential for cell functions such as maintaining the cell's shape, facilitating intracellular transport, and segregating chromosomes during cell division. This process of growth and shrinkage is known as dynamic instability. Microtubules reorganize to form spindle fibers during cell division, which play a critical role in the proper segregation of chromosomes to daughter cells.
Chemotherapy drugs like vincristine and colchicine target microtubules by binding to tubulin. This binding interferes with the dynamic instability of microtubules, particularly affecting their ability to form functional spindle fibers during mitosis. As a result, these drugs can halt cell division by preventing the proper alignment and separation of chromosomes, which is particularly useful in cancer treatment, as it targets rapidly dividing cancer cells.
Control over microtubule dynamic instability is mostly regulated by a mix of both internal and external mechanisms that govern the cell cycle, using molecules for positive and negative regulation. Additionally, drugs like vinblastine, which inhibit microtubule assembly, affect the structure and function of microtubules, with effective therapeutic use in cancer chemotherapy.