So at metaphase, we basically line up all our chromosomes along the center, as shown, and the two centrioles are found on opposite sides. And the centriole synthesize fibers known as spindle fibers. And if disjunction actually takes place correctly, what happens is each spindle fiber attaches to each side of our chromosome. So when our separation takes place, we have an equal separation of chromosomes to both sides of the cells. So these chromatids will end up on that side, and these chromatids will end up on the other side. Now, in the case of nondisjunction, during anaphase of mitosis, what can happen is a spindle fiber might incorrectly attach itself or not attach itself at all to the centromere portion of our chromosome, or the centromere might not actually divide correctly, and this can lead to the process of nondisjunction.