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a part of a chromosome that plays a fundamental role in its movement during cell division (mitosis). In the metaphase stage of mitosis, the area of the centromere within the chromosome is less dense than the chromosome’s other areas and forms a primary constriction that divides the chromosome into two sections; the position of this constriction is a basis for the classification of chromosomes. The cytoplasmic filaments (microtubules) of the spindle of cell division are attached to the centromere by their ends.
Some organisms, such as members of the genus Luzula and the scorpion, have polycentromeric chromosomes with a diffuse centromere and with the spindle filaments attached to the chromosome along its entire length. With a light microscope a cluster of chromomeres may be seen near the centromere of a chromosome during metaphase. Examination of mammalian cells with an electron microscope reveals a three-layered structure near each of the two longitudinal chromosome filaments, or chromatids. This structure is a kinetochore plate, whose interaction with the spindle filaments results in the even distribution of chromosomes among the daughter cells during cell division. Chromosomal aberrations involving the chromomere hamper the distribution of chromosomal material during mitosis and meiosis and alter the organism’s karyotype. Chromosomes that lack a centromere cannot take part in mitosis.
I. I. KIKNADZE