5.2.4—Mitosis image interpretation

Stage identification in a mitosis micrograph or root-tip section is an evidence-matching task: inspect chromosome position and state first, then use nuclear-envelope and cell-separation clues when they are visible, and assign the PMAT stage only when the combined evidence fits.

1. Check the specimen and evidence: Confirm that the field is a suitable stained root-tip or other mitotic preparation. Note the cell orientation, image quality and whether the nucleus, chromosome group or cell boundary is actually visible; do not infer a hidden feature from an unclear image.
2. Inspect chromosome condensation: Look for distinct condensed chromosomes, chromosomes arranged in a line at the equator, sister chromatids separated into two groups, or chromosomes gathered at poles and beginning to decondense.
3. Inspect nuclear and spindle clues: If resolvable, check whether the nuclear envelope is breaking down or absent, whether spindle fibres are guiding an equatorial arrangement or poleward movement, and whether nuclear envelopes are reforming. These clues support the chromosome evidence rather than replacing it.
4. Match the stage: Prophase is condensation and preparation for movement; metaphase is equatorial alignment; anaphase is separated chromatids moving towards opposite poles; telophase is pole arrival with decondensation and reforming nuclei. Cytokinesis or a new cell partition is supporting evidence for completion of division, not a separate PMAT stage.
5. Cross-check before deciding: Use at least two compatible observations where possible—for example, equatorial alignment plus spindle attachment for metaphase, or two separated chromosome groups plus poleward movement for anaphase. Compare neighbouring cells only as context: a root-tip field contains cells at different stages, not one shared stage.

The decisive evidence changes through PMAT: chromosomes first become compact and movable, then align, then separate, and finally reach opposite poles while nuclei reform. This sequence explains why a cell with joined chromatids at the equator is not yet in anaphase, whereas two chromosome groups moving apart are evidence for anaphase.

Do not identify a stage from one vague shape, cell size or stain intensity alone. Section angle, overlap, image resolution and an obscured nuclear envelope can hide useful clues, so report only what the image supports and use the strongest visible combination. The ordered PMAT map belongs to card 4568; this card teaches how to apply it to an image or slide.