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There are several well known examples in primate chromosomes where the centromere position is different from the human centromere of the same chromosome and is thought to be evolutionary new centromeres. [37] Centromere repositioning and the formation of evolutionary new centromeres has been suggested to be a mechanism of speciation. [39]
In cell biology, the centrosome (Latin centrum 'center' + Greek sōma 'body') (archaically cytocentre [1]) is an organelle that serves as the main microtubule organizing center (MTOC) of the animal cell, as well as a regulator of cell-cycle progression. The centrosome provides structure for the cell.
Centromere placement on the chromosome can be characterized by four main arrangements, either metacentric, submetacentric, acrocentric, or telocentric. Both of these properties (i.e., the length of chromosomal arms, and the placement of the chromosomal centromere) are the main factors for creating structural homology between chromosomes.
Centromeres are the sites where spindle fibers attach to newly replicated chromosomes in order to segregate them into daughter cells when the cell divides. Each eukaryotic chromosome has a single functional centromere that is seen as a constricted region in a condensed metaphase chromosome.
However, due to a lack of full centromere assemblies, base-level understanding of satellite array variation and evolution has remained weak. [5] For example, minisatellite DNA is a short region (1-5 kb) of repeating elements with length >9 nucleotides.
Image of kinetochores in pink. A kinetochore (/ k ɪ ˈ n ɛ t ə k ɔːr /, /-ˈ n iː t ə k ɔːr /) is a flared oblique-shaped protein structure associated with duplicated chromatids in eukaryotic cells where the spindle fibers, which can be thought of as the ropes pulling chromosomes apart, attach during cell division to pull sister chromatids apart. [1]
The sister chromatids will be distributed to each daughter cell at the end of the cell division. Whereas if the chromosome is isobrachial (centromere at centre and arms of equal length), the p and q system is meaningless. At either end of a chromosome is a telomere, a cap of DNA that protects the rest of the chromosome from damage.
In prophase of mitosis, specialized regions on centromeres called kinetochores attach chromosomes to spindle fibers. The monocentric chromosome is a chromosome that has only one centromere in a chromosome and forms a narrow constriction. Monocentric centromeres are the most common structure on highly repetitive DNA in plants and animals. [1]