pro·phase   (prō'fāz')    n.   The first stage of mitosis, during which the chromosomes condense and become visible, the nuclear membrane breaks down, and the spindle apparatus forms at opposite poles of the cell. The first stage of meiosis, constituted by a series of events that include the thickening and coiling of the chromosomes, synapsis of homologous chromosomes, tetrad formation, and crossing over. pro·pha'sic (-fā'zĭk) adj.

Main Entry: pro·phase
Pronunciation: -"fAz
Function: noun
1 : the initial stage of mitosis and of the mitotic division of meiosis characterizedby the condensation of chromosomes consisting of two chromatids, disappearance of the nucleolus and nuclear membrane, and formation of the mitotic spindle
2 : the initial stage ofthe first division of meiosis in which the chromosomes become visible, homologous pairs of chromosomes undergo synapsis and crossing-over, chiasmata appear, chromosomes condense with homologues visibleas tetrads, and the nuclear membrane and nucleolus disappear and which is divided into the five consecutive stages leptotene, zygotene, pachytene, diplotene, and diakinesis —pro·pha·sic /(')prO-'fA-zik/ adjective

prophase pro·phase (prō'fāz')
n.

1. The first stage of mitosis, during which the chromosomes condense and become visible, the nuclear membrane breaks down, and the spindle apparatus forms at opposite poles of the cell.

2. The first stage of meiosis, during which the DNA replicates, homologous chromosomes undergo synapsis, chiasmata form, and the chromosomes contract.

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pro·pha'sic (-fā'zĭk) adj.