During which phase are spindle fibers fully attached to chromosomes?

During metaphase, spindle fibers are fully attached to the chromosomes, aligning them at the cell's equatorial plane, also known as the metaphase plate. This alignment is crucial for the proper separation of chromosomes during the subsequent phase of cell division. The spindle fibers originate from the centrosomes and connect to the kinetochores, which are protein structures on the chromosome's centromeres.

The correct functioning of spindle fibers is essential to ensure that each daughter cell receives an identical set of chromosomes when the cell divides. During metaphase, any issue with spindle attachment can lead to unequal chromosome distribution, which can result in conditions such as aneuploidy in the daughter cells. Thus, the specific role of spindle fibers during metaphase highlights its significance in the overall process of mitosis.