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Prophase I

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Definition

noun

The first stage in the first meiotic division of meiosis characterized by having five sub-stages namely leptotene, zygotene, pachytene, diplotene and diakinesis, and essential mainly for the exchange of DNA between homologous chromosomes via a process called homologous recombination and the crossover at chiasma(ta) between non-sister chromatids


Supplement

Meiosis is a specialized form of cell division that ultimately gives rise to non-identical sex cells. There are two successive nuclear divisions: meiosis I and meiosis II. Each of them has four major phases. These are prophase, metaphase, anaphase and telophase. Each of these phases is designated as I or II depending where it occurs, i.e. in meiosis I or in meiosis II.

Prophase I is the first stage in meiosis I. This stage is characterized by having five sub-stages namely leptotene, zygotene, pachytene, diplotene and diakinesis. Prophase I highlights the exchange of DNA between homologous chromosomes via a process called homologous recombination and the crossover at chiasma(ta) between non-sister chromatids. Thus, this stage is important to increase genetic variation. This stage then ends with the disintegration of the nucleolus and the nuclear membrane. Prophase I precedes metaphase I, a stage that features homologous chromosomes aligning along a single plane in the center of the cell.


See also:

Mentioned in:

  • DNA replication
  • Chromosomal crossover