16 InterphaseThis cell is shown, as this is how all cells look before mitosis. Please be aware that Interphase is a phase of the cell cycle, but NOT a stage of mitosis.
17 Mitosis - Early Prophase To begin mitosis, the nuclear membrane breaks down, while the chromosomes shorten and thicken (here, a chromosome is two chromatids, bound at a point called the centromere, making an "X" shape). The other structures important for mitosis are also forming (i.e. the centrioles).
18 Mitosis - MetaphaseThe spindle has now formed and the nuclear membrane has broken down. The chromosomes are lined up along the cell's center and are attached to the spindle fibers. When the individual chromatids (½ of the "X") are separated from the chromosome (the "X"), they are now each referred to as a chromosome (i.e. In metaphase, the chromosome, composed of two chromatids, separates into the individual chromatids, which are then renamed chromosomes).
19 Mitosis - AnaphaseThe newly formed chromosomes are pulled along the spindle toward opposite poles of the cell.
20 Mitosis - TelophaseThe chromosomes have finished their migration to the poles. The spindle has broken down and disappeared. The cell membrane pinches in (forms a cleavage furrow) along the center creating two separate cells . At this time, the chromosomes uncoil and become less visible (as they are during Interphase), the nuclear membrane reforms. The division of the cytoplasm is called cytokinesis. The division of the nucleus is Mitosis. At the end of Telophase, the cell reenters Interphase.
26 Alabama State University, Math, Science Partnership, Winter,2013 Prepared by: Dr. Debbie Payne, Ruth H. Liddell, Shirley K. ScarbroughAlabama State University, Math, Science Partnership, Winter,2013