Mitosis or karyokinesis, along with cytokinesis comprise the M phase or the mitosis phase of the cell cycle. During mitosis, the parent cell divides into two daughter cells, which are not only identical to each other but also to the parent cell. Mitosis is also known as equational division, as both the parent and the progeny cells have the same number of chromosomes. Mitosis is divided into four stages of nuclear division, namely prophase, metaphase, anaphase and telophase.
During prophase, the untangling of the chromatin takes place, and each chromosome has two chromatids attached together at the centromere. The centrioles move to the opposite ends of the cell to initiate the formation of the spindle fibres. The nucleolus, endoplasmic reticulum, golgi complexes and nuclear envelope disappear.
During metaphase, the nuclear membrane disintegrates, resulting in the scattering of chromosomes in the cytoplasm as two sister chromatids bound by a centromere. Each centromere has a small disc-shaped structure on its surface, called the kinetochore. Spindle fibres attach to the kinetochores of the chromosomes and the chromosomes move towards the equator. The plane of alignment of the chromosomes during this phase is known as the metaphase plate.
During anaphase, the centromere of each chromosome splits and the chromatids separate. They slowly move towards the opposite poles. The centromeres of the chromatids face the pole, while their arms trail behind.
During telophase, the chromosomes cluster at opposite poles and decondense to form a mass of chromatin material. A nuclear envelope is formed around each chromosome cluster, and the organelles - nucleolus, golgi complex and endoplasmic reticulum reappear at both poles. Thus, a cell segregates its chromosomes into two identical daughter nuclei.