Chromosome behaviour in mitosis · ⁨有丝分裂中染色体的行为⁩

The four stages of mitosis

• Mitosis runs through four stages — remember them in order: P · M · A · T.
• In each, the chromosomes do something you can recognise under a microscope.
• After mitosis, the whole cell splits in cytokinesis 胞质分裂.

Prophase 前期 and metaphase 中期

• Prophase: chromosomes coil up and become visible (as two sister chromatids); the nuclear envelope 核膜 breaks down; a spindle 纺锤体 of fibres forms.
• Metaphase: chromosomes line up along the middle (the equator); spindle fibres attach to each centromere.

A replicated chromosome with two sister chromatids

Anaphase 后期 and telophase 末期

• Anaphase: the centromeres split, and the sister chromatids are pulled to opposite poles of the cell.
• Telophase: a full set of chromosomes reaches each pole; a new nuclear envelope forms around each set, giving two nuclei.

The four stages of mitosis

Cytokinesis

• The cytoplasm now divides:
  • in an animal cell, the membrane pinches inwards to split the cell.
  • in a plant cell, a new cell wall forms across the middle.
• The result: two genetically identical daughter cells.

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