WANI Dictionary

Prophase

Prophase is the first stage of mitosis and meiosis.

In a narrow definition, prophase is the first phase of mitosis, and the first stage of meiosis is called prophase I.

Major events during prophase include:

• Chromosomes become visible under the light microscope (both mitosis and meiosis).
• In the prophase of meiosis I (prophase I), homologous chromosomes pair up and form chiasmata, and crossing over takes place.
• Spindle begins to form.

In mitosis, as the spindle formation is completed, nuclear envelope disintegrates, and the spindle microtubules bind to the chromosomes at the kinetochores. When prometaphase is defined, these events take place during prometaphase. When prophase is followed by metaphase, these events take place during prophase.

Definitions in the literature

• the first stage of mitosis, in which the chromosomes first become visible in the light microscope as thickened, condensed threads and the spindle begins to form; ... Also, the first stage of meiosis: In meiosis I, the homologous chromosomes pair up, ... [1].
• Stage of mitosis in which the chromosomes contact and become visible, the cytoskeleton breaks down, and the mitotic spindle begins to form [2].