prophase

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prophase

 [pro´fāz]
the first stage of cell replication in either meiosis or mitosis.

pro·phase

(prō'fāz),
The first stage of mitosis or meiosis, consisting of linear contraction and increase in thickness of the chromosomes (each composed of two chromatids) accompanied by migration of the two daughter centrioles and their asters toward the poles of the cell. In meiosis, prophase is complex and can be subdivided into stages: preleptotene, leptotene, zygotene, pachytene, diplotene, and diakinesis.
[G. prophasis, from prophainō, to foreshadow]

prophase

/pro·phase/ (-fāz) the first stage in cell reduplication in either meiosis or mitosis.

prophase

(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, 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.

prophase

[prō′fāz]
Etymology: Gk, pro + phasis, appearance
the first of four stages of nuclear division in mitosis and in each of the two divisions of meiosis. In mitosis the chromosomes progressively shorten and thicken to form individually recognizable elongated double structures composed of two chromatids held together by a centromere. The nucleolus and nuclear membrane disappear, the spindle and polar bodies are formed, and the chromosomes begin to migrate toward the midplane of the developing spindle. In the first meiotic division, prophase is complex and subdivided into five stages: leptotene, zygotene, pachytene, diplotene, and diakinesis. In the second meiotic division the same processes occur as in mitotic prophase. See also anaphase, interphase, meiosis, metaphase, mitosis, telophase.
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Prophase

pro·phase

(prō'fāz)
The first stage of mitosis or meiosis, consisting of linear contraction and increase in thickness of the chromosomes (each composed of two chromatids) accompanied by migration of the two daughter centrioles and their asters toward the poles of the cell.
[G. prophasis, from prophainō, to foreshadow]

prophase

The first stage in cell division by MITOSIS and MEIOSIS, during which CHROMATIN coils up to form chromosomes.

prophase

the first stage of nuclear division (MITOSIS and MEIOSIS) in which the chromosomes coil and thicken and become visible with the optical microscope, condensing onto the inner wall of the NUCLEAR MEMBRANE. As the stage proceeds, the NUCLEOLUS disappears from view and the nuclear membrane disintegrates, leaving a clear area at the edge of the nucleus which contains the CENTROSOME.

Meiosis has a much more complicated prophase than mitosis, and can be summarized thus:

  1. (a) meiosis has two prophases, the first one complex (see below).the second rather similar to prophase in mitosis.
  2. (b) prophase 1 of meiosis can be divided into five substages: LEPTOTENE, ZYGOTENE, PACHYTENE, DIPLOTENE and DIAKINESIS. The essential processes occurring are: (i) pairing of homologous chromosomes, (ii) pairing of nonsister CHROMATIDS forming chiasmata with eventual CROSSING OVER.

prophase

the first stage of cell replication in either meiosis or mitosis.