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Prophase is the first step of cell division in mitosis. As it occurs after G2 of interphase, DNA has been already replicated when prophase begins. [1] Fluorescence microscope image of two mouse cell nuclei in prophase (scale bar is 5 μm).
Chromosomal crossover, or crossing over, is the exchange of genetic material during sexual reproduction between two homologous chromosomes' non-sister chromatids that results in recombinant chromosomes. It is one of the final phases of genetic recombination, which occurs in the pachytene stage of prophase I of meiosis during a process called ...
The leptotene stage, also known as leptonema, is the first of five substages of prophase I during meiosis, the specialized cell division that reduces the chromosome number by half to produce haploid gametes in sexually reproducing organisms.
At the onset of prophase, chromatin fibers condense into discrete chromosomes that are typically visible at high magnification through a light microscope. In this stage, chromosomes are long, thin, and thread-like. Each chromosome has two chromatids. The two chromatids are joined at the centromere. Gene transcription ceases during prophase and ...
Zygotene (from greek "paired threads" [1]) is the second stage of prophase I during meiosis, the specialized cell division that reduces the chromosome number by half to produce haploid gametes. It follows the Leptotene stage and is followed by Pachytene stage.
The identical sister chromatids have not yet condensed into the densely packaged chromosomes visible with the light microscope. This will take place during prophase I in meiosis. Growth 2 (G 2) phase: G 2 phase as seen before mitosis is not present in meiosis. Meiotic prophase corresponds most closely to the G 2 phase of the mitotic cell cycle.
Chromosomal crossover involves recombination between the paired chromosomes inherited from each of one's parents, generally occurring during meiosis. [citation needed] During prophase I (pachytene stage) the four available chromatids are in tight formation with one another.
Synapsis or Syzygy is the pairing of two chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them. Synapsis takes place during prophase I of meiosis. When homologous chromosomes synapse, their ends are first attached to the nuclear envelope.