Final answer:
The region on a chromosome where microtubules attach during cell division is called the kinetochore.
Step-by-step explanation:
The region of a chromosome where microtubules connect to a chromosome pair during cell division is known as the kinetochore. This protein complex forms in the centromeric region and plays a crucial role during mitosis and meiosis. At this site, the mitotic spindle microtubules attach to either side of the sister chromatids, ensuring that each new cell receives one copy of each chromosome when the cell divides.
During stages like prometaphase, the kinetochore is essential as it attracts and binds the spindle microtubules from the centrosomes. These microtubules provide the force necessary to pull the sister chromatids apart to opposite poles during anaphase, which is critical for proper chromosome segregation.