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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).
In eukaryotes, the cell cycle consists of four main stages: G 1, during which a cell is metabolically active and continuously grows; S phase, during which DNA replication takes place; G 2, during which cell growth continues and the cell synthesizes various proteins in preparation for division; and the M phase, during which the duplicated ...
G 2 phase ends with the onset of prophase, the first phase of mitosis in which the cell’s chromatin condenses into chromosomes. G 2 phase is a period of rapid cell growth and protein synthesis during which the cell prepares itself for mitosis.
Prophase is the initial phase when spindle fibers appear that function to move the chromosomes toward opposite poles. This spindle apparatus consists of microtubules, microfilaments and a complex network of various proteins. During metaphase, the chromosomes line up using the spindle apparatus in the middle of the cell along the equatorial plate.
The first stage of prophase I is the leptotene stage, also known as leptonema, from Greek words meaning "thin threads". [18]: 27 In this stage of prophase I, individual chromosomes—each consisting of two replicated sister chromatids—become "individualized" to form visible strands within the nucleus.
Using different types of genetic studies, it has been established that diverse kinds of defects are able to activate the SAC: spindle depolymerization, [8] [9] the presence of dicentric chromosomes (with two centromeres), [10] centromeres segregating in an aberrant way, [11] defects in the spindle pole bodies in S. cerevisiae, [12] defects in ...
Meiotic sex chromosome inactivation only happens in male, which may partially be the reason why only Spo11 mutant spermatocytes but not oocytes fail to transition from prophase I to metaphase I. [3] [8] However the asynapsis does not happen only within sex chromosomes, and such transcription regulation was suspended until it was further ...
In an experiment using radiation hybrid mapping on wheat's (Triticum aestivum L.) 3B chromosome, crossing over and DNA repair were found to occur predominantly in the same regions. [13] Furthermore, crossing over has been correlated to occur in response to stressful, and likely DNA damaging, conditions. [14] [15]