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Metaphase (from Ancient Greek μετα- 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 at their most condensed in anaphase). [1]
Ndt80 stimulates the expression of the B-type cyclin Clb-1, which greatly interacts with Cdk1 during meiotic divisions. [24] Active complexes of Clb-1 with Cdk1 play a large role in triggering the events of the first meiotic division, and their activity is restricted to meiosis 1. [25]
This is an accepted version of this page This is the latest accepted revision, reviewed on 7 December 2024. Cell division producing haploid gametes For the figure of speech, see Meiosis (figure of speech). For the process whereby cell nuclei divide to produce two copies of themselves, see Mitosis. For excessive constriction of the pupils, see Miosis. For the parasitic infestation, see Myiasis ...
Left: 1 start helix "solenoid" structure. Right: 2 start loose helix structure. Note: the histones are omitted in this diagram - only the DNA is shown. With addition of H1, during mitosis the beads-on-a-string structure can coil into a 30 nm-diameter helical structure known as the 30 nm fibre or filament. The precise structure of the chromatin ...
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.
It is visible on a chromosome during the prophase of meiosis and mitosis. Giant banded chromosomes resulting from the replication of the chromosomes and the synapsis of homologs without cell division is a process called endomitosis. These chromosomes consist of more than 1000 copies of the same chromatid that are aligned and produce alternating ...
There are two popular and overlapping theories that explain the origins of crossing-over, coming from the different theories on the origin of meiosis.The first theory rests upon the idea that meiosis evolved as another method of DNA repair, and thus crossing-over is a novel way to replace possibly damaged sections of DNA. [9]
Following recombination, chromosome segregation occurs as indicated by the stages metaphase I and anaphase I in the meiosis diagram. Different pairs of chromosomes segregate independently of each other, a process termed “independent assortment of non-homologous chromosomes”. This process results in each gamete usually containing a mixture ...