Metaphase is the third phase of mitosis, which is the process of cell division that separates the duplicated genetic material carried in the nucleus of a parent cell into two identical daughter cells. During metaphase, the cells chromosomes align themselves in the middle of the cell through a type of cellular "tug of war". Prior to metaphase, protein formations called kinetochores form around the centromere, and long protein filaments called kinetochore microtubules extend from poles on either end of the cell and attach to the kinetochores. During metaphase, the kinetochore microtubules pull the sister chromatids back and forth until they align along the equator of the cell, called the equatorial plane. At this stage, the chromosomes are distinguishable when viewed through a microscope, and they are used in karyotyping, a laboratory technique for identifying chromosomal abnormalities. There is an important checkpoint in the middle of mitosis, called the metaphase checkpoint, during which the cell ensures that all of the chromosomes are properly aligned and that the kinetochores are correctly attached before proceeding to anaphase.