Final answer:
The centrosome, not the centromere, nucleates microtubules for the mitotic spindle assembly. During mitosis and meiosis, centrosomes act as microtubule-organizing centers. The kinetochore, related to the centromere, binds microtubules but is not the origin site for their growth.
Step-by-step explanation:
The statement that the centromere nucleates the microtubules of the mitotic spindle is false. The correct structure that nucleates the microtubules and thereby is responsible for the assembly of the mitotic spindle is the centrosome, not the centromere. The centrosome acts as a microtubule-organizing center and is composed of two centrioles, which begin to migrate to opposite sides of the cell during prophase. Microtubules extend from these centrosomes and form the mitotic spindle, essential for the separation of chromosomes during mitosis and meiosis.
The kinetochore is a protein structure located on the centromere region of the chromosome that attracts and binds to the mitotic spindle microtubules, which is essential for the accurate segregation of chromosomes. Therefore, when asked the mitotic spindles arise from which cell structure, the correct answer is b. centrosome.