Final answer:
The described stage is anaphase, where centromeres divide and sister chromatids, now individual chromosomes, are pulled to opposite cell poles by the shortening of spindle fibers.
Step-by-step explanation:
The stage where the centromeres divide to form two chromosomes, and the spindle pulls sister chromosomes to opposite poles is known as anaphase. During this phase, sister chromatids, now called chromosomes, move to opposite ends of the cell as the spindle fibers shorten. This action ensures that each pole of the cell ends up with a complete set of chromosomes, and is critical for the equal division of genetic material between the two future daughter cells. In the context of meiosis, this process would be referred to as anaphase II, which follows a similar mechanism to separate sister chromatids.