centromernél

The centromere is the region of a chromosome that serves as the attachment site for kinetochores and is essential for accurate chromosome segregation during cell division. Centromeres vary in position and size across species, and the functional centromere is not defined by a single DNA sequence in most eukaryotes.

Centromeric chromatin is specialized and contains nucleosomes that replace standard histone H3 with the centromere-specific variant CENP-A. This epigenetic feature helps mark the centromere and recruits other kinetochore components. In many organisms, centromeric DNA is repetitive, yet the sequence alone does not determine centromere identity.

The kinetochore is a multiprotein complex assembled at the centromere. It links centromeric chromatin to spindle microtubules and drives chromosome movement during anaphase. The inner kinetochore interfaces with centromeric chromatin, while the outer kinetochore attaches to microtubules and participates in spindle checkpoint signaling.

Chromosome identity at the centromere is largely epigenetic. Some organisms have regional centromeres spanning large chromosomal regions; others have point centromeres with defined DNA motifs. Neocentromeres can form at nontraditional sites, illustrating that centromere function can be specified independently of primary DNA sequence.

From an evolutionary perspective, centromeres show rapid changes in DNA sequence and protein composition, with phenomena such as centromere drive and rapid CENP protein evolution. Functionally, centromere integrity is crucial for genome stability, and missegregation contributes to aneuploidy and cancer.