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The mitotic spindle checkpoint verifies that all the chromosomes are aligned properly on the metaphase plate and prevents premature entry into anaphase.Chromosomes lined up on the metaphase plate. Two views with the metaphase plate rotated 60°.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 at their most condensed in anaphase).[1] These chromosomes, carrying genetic information, align in the equator of the cell between the spindle poles at the metaphase plate, before being separated into each of the two daughter nuclei. This alignment marks the beginning of metaphase.[2] Metaphase accounts for approximately 4% of the cell cycle's duration.[citation needed]
In metaphase, microtubules from both duplicated centrosomes on opposite poles of the cell have completed attachment to kinetochores on condensed chromosomes. The centromeres of the chromosomes convene themselves on the metaphase plate, an imaginary line that is equidistant from the two spindle poles.[3] This even alignment is due to the counterbalance of the pulling powers generated by the opposing kinetochore microtubules,[4] analogous to a tug-of-war between two people of equal strength, ending with the destruction of B cyclin.[5]
In order to prevent deleterious nondisjunction events, a key cell cycle checkpoint, the spindle checkpoint, verifies this evenly balanced alignment and ensures that every kinetochore is properly attached to a bundle of microtubules and is under balanced bipolar tension. Sister chromatids require active separase to hydrolyze the cohesin that bind them together prior to progression to anaphase. Any unattached or improperly attached kinetochores generate signals that prevent the activation of the anaphase promoting complex (cyclosome or APC/C), a ubiquitin ligase which targets securin and cyclin B for degradation via the proteosome. As long as securin and cyclin B remain active, separase remains inactive, preventing premature progression to anaphase.
^"Chromosome condensation through mitosis". ScienceDaily. Retrieved 12 June 2007.
^Alberts, Bruce; Hopkin, Karen; Johnson, Alexander; Morgan, David; Raff, Martin; Roberts, Keith; Walter, Peter (2019). Essential cell biology (Fifth ed.). New York London: W. W. Norton & Company. p. 632–633. ISBN 9780393680393.
^"Metaphase plate". Biology Dictionary. Biology Online. Retrieved 9 December 2012.
^"Metaphase". Nature Education. Retrieved 9 December 2012.
^"The Cell Cycle". Kimball's Biology Pages. Archived from the original on 19 November 2012. Retrieved 9 December 2012.
Metaphase (from Ancient Greek μετα- (meta-) beyond, above, transcending and from Ancient Greek φάσις (phásis) 'appearance') is a stage of mitosis in the...
homologous chromosome pairs along the metaphase plate during metaphase I and orientation of sister chromatids in metaphase II, this is the subsequent separation...
stages are preprophase (specific to plant cells), prophase, prometaphase, metaphase, anaphase, and telophase. During mitosis, the chromosomes, which have...
copies are now called sister chromatids. During metaphase, the X-shaped structure is called a metaphase chromosome, which is highly condensed and thus...
follows prophase and precedes metaphase. In metaphase, the centromeres of the chromosomes align themselves on the metaphase plate (or equatorial plate)...
Prometaphase is the phase of mitosis following prophase and preceding metaphase in eukaryotic somatic cells. In prometaphase, the nuclear membrane breaks...
solution, which swells them and spreads the chromosomes Arresting mitosis in metaphase by a solution of colchicine Squashing the preparation on the slide forcing...
φάσις (phásis) 'appearance') is the stage of mitosis after the process of metaphase, when replicated chromosomes are split and the newly-copied chromosomes...
spindle checkpoint, also known as the metaphase-to-anaphase transition, the spindle assembly checkpoint (SAC), the metaphase checkpoint, or the mitotic checkpoint...
poles of the mitotic spindle apparatus. Following the transition from metaphase to anaphase, the sister chromatids separate from each other, and the individual...
membrane monoamine transporter (PMAT) Four phases of mitosis: prophase, metaphase, anaphase, and telophase. Prophase: Chromatin into chromosomes, the nuclear...
controlling the G2/M checkpoint. The metaphase checkpoint is a fairly minor checkpoint, in that once a cell is in metaphase, it has committed to undergoing...
system is a regulatory system that restrains progression through the metaphase-to-anaphase transition. The Mad2 gene was first identified in the yeast...
During oocyte development, high metaphase promoting factor (MPF) activity causes mammalian oocytes to arrest at the metaphase II stage until fertilization...
restriction checkpoint or Major Checkpoint; the G2/M checkpoint; and the metaphase-to-anaphase transition, also known as the spindle checkpoint. Progression...
(heterochromatin). Higher-level DNA supercoiling of the 30 nm fiber produces the metaphase chromosome (during mitosis and meiosis). Many organisms, however, do not...
In metaphase I of meiosis I, the pairs of homologous chromosomes, also known as bivalents or tetrads, line up in a random order along the metaphase plate...
the oocyte, causing meiosis to resume. Meiosis then proceeds to second metaphase, where it pauses again until fertilization. Luteinizing hormone also stimulates...
An image of a newt lung cell stained with fluorescent dyes during metaphase. The mitotic spindle can be seen, stained green, attached to the two sets...
photographic representation of the entire chromosome complement. The metaphase chromosomes are treated with trypsin (to partially digest the chromosome)...
and into the fallopian tube and triggers the oocyte to divide and enter metaphase of meiosis II (46 or 2n chromosome) and extrude its first polar body....
been observed in both the cell's meiotic spindle regions during metaphase I and metaphase II of meiosis. CGFDs have not been observed in feline, equine...
chromosome along its entire length and move broadside to the pole from the metaphase plate. Holocentric chromosomes are also termed holokinetic, because, during...
hybridization of the two resultant samples in a 1:1 ratio to a normal metaphase spread of chromosomes, to which the labelled DNA samples will bind at...
DNA synthesis, occurring in the S phase (annotated as S) of the cell cycle. This interval includes the G2 phase and metaphase (annotated as "Meta.")....
Karyotyping generally combines light microscopy and photography in the metaphase of the cell cycle, and results in a photomicrographic (or simply micrographic)...
sides of the centromere; the congressed chromosome then oscillates at the metaphase plate until anaphase onset releases cohesion of the sister chromatids...
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