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The cellular spindle apparatus includes the spindle microtubules, associated proteins, which include kinesin and dynein molecular motors, condensed chromosomes, and any centrosomes or asters that may be present at the spindle poles depending on the cell type. [4] The spindle apparatus is vaguely ellipsoid in cross
The spindle checkpoint, or SAC (for spindle assembly checkpoint), also known as the mitotic checkpoint, is a cellular mechanism responsible for detection of: correct assembly of the mitotic spindle; attachment of all chromosomes to the mitotic spindle in a bipolar manner; congression of all chromosomes at the metaphase plate.
These microtubules form direct connections with the kinetochores in the mitotic spindle. Each K fiber is composed of 20–40 parallel microtubules, forming a strong tube which is attached at one end to the centrosome and on the other to the kinetochore, located in the center of each chromosome.
Astral microtubules anchor the spindle poles to the cell membrane. Microtubule polymerization is nucleated at the microtubule organizing center . An aster is a cellular structure shaped like a star , consisting of a centrosome and its associated microtubules during the early stages of mitosis in an animal cell.
After the chromosomes line up in the middle of the cell, the spindle fibers will pull them apart. The chromosomes are split apart while the sister chromatids move to opposite sides of the cell. [29] As the sister chromatids are being pulled apart, the cell and plasma are elongated by non-kinetochore microtubules. [30]
In the absence of the centrioles, the microtubules of the spindle are focused by motors, allowing the formation of a bipolar spindle. Many cells can completely undergo interphase without centrioles. [10] Unlike centrioles, centrosomes are required for survival of the organism. Cells without centrosomes lack radial arrays of astral microtubules ...
An array of microtubules can arrange themselves in a pinwheel structure to form the basal bodies, which can lead to the formation of microtubule arrays in the cytoplasm or the 9+2 axoneme. Other arrangements range from fungi spindle pole bodies to the eukaryotic chromosomal kinetochores (flat, laminated plaques). MTOCs can be freely dispersed ...
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 chromosomes move to opposite poles during anaphase and remain attached to the spindle fibers by their centromeres.