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Multicellular organisms grow by expansion and division and may be very rapid in young tissue. When continuous replacement of cells is necessary mature tissue may also divide rapidly as in a layer of intestine called the epithelial. In plants certain regulators of growth stimulate new cell division. Meiosis, mitosis and amitosis are examples of this.
Cells formed by meiosis is the result of fertilization restoring the correct chromosome complement. This consist of two divisions which the chromosomes replicate only once. Here the stages prophase, metaphase, and anaphase can be recognized. But during prophase homologous chromosomes attract each other and are paired forming bivalents.
At the end of prophase genetic material may be exchanged between the chromotids of the homologous chromosomes.