Stages of mitosis: Metaphase
In metaphase, the second stage of mitosis:
- The nuclear envelope disappears between late prophase and metaphase.
- The centrosomes which were migrating during prophase are now at opposite poles.
- The mitotic spindle is fully formed.
- The mitotic spindle attaches itself to the centromeres of the chromosome.
- The mitotic spindle retracts and arranges the chromosomes at the equator of the cell, midway between the two centrosomes.
The mitotic spindle will now be able to separate the sister chromatids during anaphase.
Since each sister chromatid is attached to just one set of spindle fibres, retraction of the fibres pulls only one sister chromatid on each chromosome to each pole.
This ensures the daughter cells have the same number of chromosomes.