Final answer:
During metaphase of mitosis, sister chromatids line up at the metaphase plate and are ready to be separated into two new cells.
Step-by-step explanation:
The stage in question is metaphase, which is the second stage of mitosis. During metaphase, the sister chromatids are aligned at the metaphase plate, a plane midway between the two poles of the cell. These sister chromatids, which are at their most visible under the microscope at this point, are tightly connected by cohesin proteins.
Spindle microtubules from the centrosomes at each pole of the cell are attached to the kinetochores of the sister chromatids and are prepared to pull them apart into each of the two new cells that will form following cell division.