Final answer:
The microtubule-organizing centers that form the mitotic spindle in animal cells are known as Centrosomes, which contain pairs of centrioles. These structures are essential for mitosis, facilitating the formation of the mitotic spindle.
Step-by-step explanation:
The two microtubule-organizing centers (MTOCs) that form the mitotic spindle of animal cells are called Centrosomes. These centrosomes are crucial for the process of cell division, specifically during mitosis and meiosis. Each centrosome contains a pair of centrioles, with each centriole being a cylinder composed of nine triplets of microtubules. As cells enter into prophase, the centrosomes move apart from one another, and microtubules begin to extend from them, forming the mitotic spindle.
Centrosomes are different from kinetochores and centromeres. Kinetochore microtubules attach to the kinetochores, which are specific protein structures associated with the centromeres of condensed chromosomes, aiding in their segregation during cell division. Chromatids are duplicated chromosomes that are visible and paired during the early stages of cell division but do not serve as organizing centers for microtubules