Mitosis - Stages of Mitosis

In this video we are will look at mitosis, including the names of the key stages: interphase, prophase, metaphase, anaphase, telophase and cytokinesis. Mitosis is the process of cell division that produces identical copies of cells, and is involved in growth, cell repair and asexual reproduction. When cells divide by mitosis, the number of cells increases, and hence the organism grows. Different organisms have different numbers of chromosomes. A chromosome is made up of two chromatids; one from the mother and one from the father. During interphase, the chromosomes duplicate and become two identical chromatids, joined at the centromere. So in humans, it has gone from the normal 46 to 92. During prophase, the chromosomes condense in the nucleus, and the spindle fibres form in the cytoplasm. During metaphase the nuclear membrane breaks apart, the spindle fibres attach to the chromosomes and the chromosomes line up at the equator of the cell. In anaphase, the spindle fibres shorten and the centromere divides, so that each chromosome becomes two separate chromatids. During telophase the nuclear membrane forms around each set of chromosomes. The chromosomes spread back out in their ‘new’ nucleus and the spindle fibres break down. In humans, each nucleus has the normal ‘46’ chromosomes again. The final stage is cytokinesis. The cell membrane pinches in to separate the two sets of chromatids into two identical daughter cells, with the same number of chromosomes as the parent - so 46 (or 23 pairs) in humans.