DNA replicates as mitosis

Prophase I

Homologous chromosomes condense (synapsis) to form bivalents. The chromatids become coiled around each other. Non sister chromatids break and rejoin at exactly corresponding locations. This is crossing over and results in the formation of chiasmata.

Beginning of prophase I

During prophase I

Chiasmata are formed at the point the chromatids cross over.

End of prophase I

Metaphase I

The bivalents move to the equator of the cell. Which pair of chromosomes orientates to which pole is completely random (called random assortment)

Anaphase I

Each pair of chromatids moves to a pole.
N.B. Unlike mitosis, there is no division of the centromeres at this stage.

Telophase I

The pairs of chromatids reach their respective poles, the cell divides.

Prophase II

New spindle is formed and the centrioles have replicated. Nuclear membrane disintegrates.

Metaphase II

The pairs of chromatids line themselves up on the equator as in mitosis, with sister chromatids orientated toward opposite poles.

Anaphase II

The centromeres divide and the chromatids separate, migrating to opposite poles.

Telophase II

The cell divides.

Nuclear membranes and nucleoli are reformed.

The chromosomes uncoil and go into interphase.

The daughter cells have half the number of chromosomes present in the original cell.