What structure forms the mitotic spindle during mitosis?

During mitosis, the mitotic spindle is primarily formed by microtubules, which are dynamic structures made up of tubulin proteins. The microtubules assemble and organize into the spindle apparatus that is essential for separating chromosomes during cell division.

Microtubules undergo rapid polymerization and depolymerization, allowing the spindle fibers to grow and shrink as needed to precisely align and segregate the chromosomes. This action ensures that each daughter cell receives an accurate complement of chromosomes, maintaining genetic stability.

While centrioles play a role in the formation of the mitotic spindle by organizing the microtubules, they do not directly form the spindle itself. On the other hand, spindle fibers are often used interchangeably to refer to the microtubules within the spindle apparatus. However, the most direct answer regarding the primary structural component that forms the mitotic spindle is microtubules. Actin filaments, although critical for other cellular functions such as muscle contraction and cytokinesis, do not form the mitotic spindle.