Centromere

Definition

The constricted region of a eukaryotic chromosome where sister chromatids remain joined after DNA replication and to which spindle microtubules attach via the kinetochore during cell division. The centromere determines chromosome segregation fidelity and, in metacentric or submetacentric chromosomes, creates morphologically distinct short (p) and long (q) arms.

Etymology

From Greek kentron (center) + meros (part), reflecting its position as the anchor point for chromosome movement.

Example

In karyotypic studies of grasshoppers (Orthoptera), the position of the centromere—whether median (metacentric), subterminal (acrocentric), or terminal (telocentric)—is a primary diagnostic character for distinguishing species and documenting chromosomal rearrangements during speciation.

Related Terms

• kinetochore
• chromatid
• Mitosis
• Meiosis
• karyotype
• holocentric chromosome
• acrocentric
• metacentric

Usage Notes

Centromere position classifies chromosome morphology: metacentric (central), submetacentric (off-center), acrocentric (near one end), or telocentric (terminal). Some arthropods, notably certain insects and arachnids, possess holocentric chromosomes lacking a single defined centromere, with spindle attachment distributed along the chromosome length—a distinction critical for interpreting cytogenetic data and radiation resistance in these groups. The term refers to the DNA region (often repetitive satellite DNA) and associated proteins, not merely the visible constriction.