prophase

pro·phase  (prfz)

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, constituted by a series of events that include the thickening and coiling of the chromosomes, synapsis of homologous chromosomes, tetrad formation, and crossing over.

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pro·phasic (-fzk) adj.

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prophase [ˈprəʊˌfeɪz]

n

1. (Life Sciences & Allied Applications / Biology) the first stage of mitosis, during which the nuclear membrane disappears and the nuclear material resolves itself into chromosomes See also metaphase, anaphase, telophase

2. (Life Sciences & Allied Applications / Biology) the first stage of meiosis, divided into leptotene, zygotene, pachytene, diplotene, and diakinesis phases

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prophase  (prfz)

1. The first stage in the process of mitosis. Before prophase begins, the chromosomes duplicate to form two long, thin strands called chromatids. During prophase itself, the chromatids condense and thicken to form distinct bodies. Chromatids making up a single chromosome are joined at the middle in an area called the centromere. The membrane surrounding the nucleus disappears, and the spindle begins to form. In prophase and the later stages of mitosis until separation of the individual chromatids during anaphase, each chromosome consists of two chromatids, and each chromatid contains a complete copy of the genetic information belonging to the chromosome. For example, human beings have 23 pairs of chromosomes in all somatic cells, or 46 chromosomes in total. At the end of prophase, each of these 46 chromosomes contains two identical chromatids.

2. One of the two stages in meiosis that resemble prophase in mitosis. However, there are important distinctions between prophase of mitosis and prophase of meiosis. The prophase of meiosis occurring during the first meiotic division of the cell is usually called prophase I. In prophase I of meiosis, pairs of homologous chromosomes intertwine and the process called crossing over occurs as chromatids from homologous pairs of chromosomes swap genetic information. This process creates genetic diversity among the gametes formed through meiosis. In mitosis, by contrast, pairs of homologous chromosomes remain separate and there is no crossing over, since the purpose of mitosis is to produce cells with identical genetic material rather than gametes. At the beginning of prophase II of meiosis, which occurs after telophase during the first meiotic division, the chromosomes of each daughter cell are grouped together in a mass. During prophase II, the individual chromosomes of the daughter cells become distinct again and begin to prepare for the second meiotic division. If a membrane has formed around the chromosomes at the end of the first division, it disappears during prophase II. See more at meiosismitosis

Thesaurus

Noun	1.	prophase - the first stage of meiosis           diakinesis - the final stage of the prophase of meiosis diplotene - the fourth stage of the prophase of meiosis leptotene - the first stage of the prophase of meiosis meiosis, miosis, reduction division - (genetics) cell division that produces reproductive cells in sexually reproducing organisms; the nucleus divides into four nuclei each containing half the chromosome number (leading to gametes in animals and spores in plants) pachytene - the third stage of the prophase of meiosis phase of cell division - a stage in meiosis or mitosis synezesis, synizesis - the contraction of chromatin towards one side of the nucleus during the prophase of meiosis zygotene - the second stage of the prophase of meiosis
	2.	prophase - the first stage of mitosis mitosis - cell division in which the nucleus divides into nuclei containing the same number of chromosomes phase of cell division - a stage in meiosis or mitosis