Prophase
Chromosomes begin to condense, taking on the form that they are usually depicted in: four arms connected at a point. Each chromosome is, at this time, actually two identical copies. Each copy is called a chromatid.
A spindle begins to form from the centrioles. This spindle is made of fibers. The centrioles begin to separate.
Also, the membrane of the nucleus, or nuclear envelope, fragments and disperses.
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Prophase I
The activities are the same as in mitosis, except that in this cell the chromosomes attach to the membrane of the nucleus and then pair up with their corresponding chromosome.
While paired up, enzymes cut sequences of DNA (genes) from the chromosomes. These sequences are exchanged between the chromosomes, which allows for an exchange of genes between the two.
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