Chromosome behaviour in mitosis
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.
Prophase and metaphase
- Prophase: chromosomes coil up and become visible (as two sister chromatids); the nuclear envelope breaks down; a spindle of fibres forms.
- Metaphase: chromosomes line up along the middle (the equator); spindle fibres attach to each centromere.
Practice
In prophase:
Prophase: chromosomes coil up and become visible, the nuclear envelope breaks down, and the spindle forms.
Practice
During metaphase, the chromosomes:
In metaphase the chromosomes line up at the cell's equator and spindle fibres attach to each centromere.
Anaphase and telophase
- 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.
Practice
Anaphase is the stage where:
In anaphase the centromeres split and the spindle pulls the sister chromatids apart to the poles.
Practice
Put the stages of mitosis in the correct order.
PMAT: Prophase → Metaphase → Anaphase → Telophase.
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.
Practice
How does cytokinesis differ between animal and plant cells?
Animal cells split by the membrane pinching in; plant cells build a new cell wall across the centre.
You've got it
Key idea
- order: Prophase → Metaphase → Anaphase → Telophase (PMAT)
- prophase: chromosomes condense, nuclear envelope breaks, spindle forms
- metaphase: line up at the equator; anaphase: centromeres split, chromatids to poles
- telophase: two new nuclei; then cytokinesis (animal pinches, plant new wall)