The mitotic cell cycle

Learning objectives

Describe the structure of a chromosome (DNA wound around histone proteins, two sister chromatids joined at a centromere, telomeres at each end) and outline how telomeres prevent genes being lost from chromosome ends each time DNA replicates.

Outline the sequence of the cell cycle — interphase (G1 growth, S-phase DNA replication, G2 growth and preparation), mitosis and cytokinesis — and what the cell does in each.

Explain why organisms rely on mitosis, which gives genetically identical cells, to grow, to replace and repair tissues, and to reproduce asexually.

Describe what chromosomes, the spindle, the nuclear envelope and the cell surface membrane do during prophase, metaphase, anaphase and telophase in plant and animal cells, and identify these stages in photomicrographs, diagrams and root-tip squashes; counting the cells in each stage also gives a mitotic index (a practical extension that the syllabus does not name).

Outline how stem cells divide by mitosis to replace cells and repair tissues, and explain how uncontrolled cell division can lead to a tumour.