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Definition

noun, plural: centromeres

(1) The constricted region joining the two sister chromatids that make up an X-shaped chromosome.

(2) The site where kinetochore is formed.

Supplement

Centromere is important particularly during mitosis. Aside from being the region where chromatids are held and kinetochore is formed, it also serves as the point of attachment for spindle fibers when the spindle fibers are pulling the chromosomes toward the centrioles (situated on opposite poles in a cell) prior to cytokinesis.

When the centromere is not functioning properly, the chromatids do not align and separate properly, thus, resulting in the wrong number of chromosomes in the daughter cells, and conditions such as Down syndrome.

Word origin: From Latin centrum and Greek kentron + from Greek meros, part.
Related forms: centromeric (adjective).

Compare: kinetochore.
See also: chromatid.