Final answer:
Metaphase is the phase in which chromosomes line up across the center of the cell. The spindle connects the centromere of each chromosome to the two poles during cell division.
Step-by-step explanation:
During which phase of cell division do chromosomes line up across the center of the cell?
The chromosomes line up across the center of the cell during Metaphase. During metaphase, the sister chromatids of each chromosome align along the equator, forming a structure called the metaphase plate or equatorial plane. This is the second phase of cell division.
What structure connects the centromere of each chromosome to the two poles during cell division?
The Spindle is the structure that connects the centromere of each chromosome to the two poles during cell division. The spindle fibers attach to the centromere of each pair of sister chromatids and ensure that the sister chromatids will separate and move towards opposite poles when the cell divides.