Mitosis and the cell cycle
The cell cycle: interphase (G1 growth and protein synthesis; S phase DNA replication; G2 growth and checks), mitosis (nuclear division) and cytokinesis. In mitosis: prophase (chromosomes condense into two sister chromatids joined at the centromere; nuclear envelope breaks down; spindle forms), metaphase (chromosomes line up at the equator, attached to spindle fibres), anaphase (centromeres divide; chromatids pulled to opposite poles), telophase (nuclear envelopes reform). Result: two genetically identical diploid cells, for growth, repair and asexual reproduction. Mitotic index = cells in mitosis ÷ total cells. Telomeres protect chromosome ends; stem cells keep dividing; cancer results from mutations in genes controlling the cycle.
≈ 45 min