Sentromer

Centromere, sometimes rendered as sentromer in some languages, is the constricted region of a chromosome that is essential for correct segregation during cell division. It is the site where sister chromatids are held together by cohesin after DNA replication and where the kinetochore, a protein structure, assembles. During mitosis and meiosis, spindle microtubules attach to kinetochores at the centromere, enabling precise chromosome movement to opposite poles.

Centromeres show considerable variation in DNA sequence and organization. In many organisms, centromere identity is defined epigenetically by the presence of the histone variant CENP-A within centromeric nucleosomes. The region often contains satellite DNA repeats and is flanked by pericentromeric heterochromatin, which supports cohesion and proper chromosome architecture. Some yeasts possess point centromeres defined by specific DNA motifs, while most other eukaryotes have regional centromeres spanning large DNA blocks.

Maintenance of centromere identity is propagated through cell divisions by the continued incorporation of CENP-A and associated proteins, with deposition aided by chaperones such as HJURP in humans. The kinetochore forms on the centromere during late mitosis to early G1 and mediates microtubule attachment and force generation necessary for chromosome movement. Centromeres can shift evolutionarily, and functional kinetochores can arise at non-centromeric sites, creating neocentromeres.

Abnormal centromere function or cohesion defects can lead to chromosome mis-segregation and aneuploidy, contributing to cancer and congenital disorders. Despite sequence diversity, centromeres perform a conserved and essential role in chromosome inheritance.