Centromere
The centromere is a specialized DNA sequence on a chromosome that serves as the attachment point for the kinetochore, the protein complex that connects chromosomes to spindle fibers during cell division. It holds sister chromatids together after DNA replication until they are separated during anaphase. The position of the centromere determines chromosome shape and is used in chromosome classification: chromosomes may be metacentric (central), submetacentric, acrocentric, or telocentric based on centromere location.
Chromosome Types Based on Centromere Position
| Type | Centromere Position | Arm Ratio (p:q) | Example Chromosome (human) |
|---|---|---|---|
| Metacentric | Middle | ~1:1 | Chromosome 1, 3 |
| Submetacentric | Off-center | 1:1.7 to 1:3 | Chromosome 4, 9 |
| Acrocentric | Near one end | Very short p arm | Chromosome 13, 14, 15, 21, 22 |
| Telocentric | At tip | No p arm | Not found in humans |
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Related Terms
Spindle Fiber
Spindle fibers are dynamic protein structures made of microtubules that form the mitotic spindle apparatus during cell division, responsible for physically separating chromosomes to opposite poles of the cell. They originate from microtubule-organizing centers (centrosomes in animal cells) and attach to chromosomes at specialized protein complexes called kinetochores located on the centromere. Spindle fibers exert pulling forces by depolymerizing (shortening), generating the mechanical work needed to move chromosomes reliably during mitosis and meiosis.
Anaphase
Anaphase is the stage of cell division during which sister chromatids are pulled apart by shortening spindle fibers and migrate toward opposite poles of the cell. In mitosis, cohesion proteins between sister chromatids are cleaved, allowing each chromatid (now called a chromosome) to move to a pole. Anaphase is the shortest phase of mitosis and is driven by the depolymerization of spindle microtubules and motor proteins such as dynein.
Mitosis
Mitosis is the process of nuclear division in eukaryotic cells that produces two genetically identical daughter nuclei, each containing the same chromosome number as the parent cell. It is the primary mechanism of growth, tissue repair, and asexual reproduction in multicellular organisms. Mitosis proceeds through four sequential stages — prophase, metaphase, anaphase, and telophase — before the cytoplasm divides in cytokinesis.
From Latin "centrum" meaning center and Greek "meros" meaning part; the name reflects its central role in chromosome structure and its position near the middle of many chromosomes.