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Mitosis in the animal cell cycle (phases ordered counter-clockwise). Mitosis divides the chromosomes in a cell nucleus. Label-free live cell imaging of mesenchymal stem cells undergoing mitosis Onion cells in different phases of the cell cycle enlarged 800 diameters. a. non-dividing cells b. nuclei preparing for division (spireme-stage)
The eukaryotic cell cycle consists of four distinct phases: G 1 phase, S phase (synthesis), G 2 phase (collectively known as interphase) and M phase (mitosis and cytokinesis). M phase is itself composed of two tightly coupled processes: mitosis, in which the cell's nucleus divides, and cytokinesis, in which the cell's cytoplasm and cell membrane divides forming two daughter cells.
In S phase, the chromosomes are replicated in order for the genetic content to be maintained. [18] During G 2, the cell undergoes the final stages of growth before it enters the M phase, where spindles are synthesized. The M phase can be either mitosis or meiosis depending on the type of cell.
G2 is commenced by E2F-mediated transcription of cyclin A, which forms the cyclin A-Cdk2 complex. In order to proceed into mitosis, the cyclin B-Cdk1 complex (first discovered as MPF or M-phase promoting factor; Cdk1 is also known as Cdc2 in fission yeast and Cdc28 in budding yeast) is activated by Cdc25, a protein phosphatase. [1]
Mitosis in an animal cell (phases ordered counter-clockwise), with G 1 labeled at left. The G 1 phase, gap 1 phase, or growth 1 phase, is the first of four phases of the cell cycle that takes place in eukaryotic cell division. In this part of interphase, the cell synthesizes mRNA and proteins in preparation for subsequent steps leading to mitosis.
Interphase is the phase of the cell cycle in which a typical cell spends most of its life. Interphase is the "daily living" or metabolic phase of the cell, in which the cell obtains nutrients and metabolizes them, grows, replicates its DNA in preparation for mitosis, and conducts other "normal" cell functions. [1]
The cycles differ in when mitosis (growth) occurs. Zygotic meiosis and gametic meiosis have one mitotic stage: mitosis occurs during the n phase in zygotic meiosis and during the 2n phase in gametic meiosis. Therefore, zygotic and gametic meiosis are collectively termed "haplobiontic" (single mitotic phase, not to be confused with haplontic).
Stages of early mitosis in a vertebrate cell with micrographs of chromatids Metaphase (from Ancient Greek μετα- ( meta- ) beyond, above, transcending and from Ancient Greek φάσις (phásis) 'appearance') is a stage of mitosis in the eukaryotic cell cycle in which chromosomes are at their second-most condensed and coiled stage (they are ...