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.
Anaphase Events in Mitosis vs Meiosis
| Feature | Anaphase (Mitosis) | Anaphase I (Meiosis) | Anaphase II (Meiosis) |
|---|---|---|---|
| What separates | Sister chromatids | Homologous chromosomes | Sister chromatids |
| Cohesin cleavage | At centromere | Along chromosome arms | At centromere |
| Number moving to each pole | 46 chromatids (human) | 23 chromosomes (human) | 23 chromatids (human) |
| Driving force | Kinetochore microtubules shorten | Kinetochore microtubules shorten | Same as mitosis |
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Related Terms
Metaphase
Metaphase is the stage of cell division in which chromosomes reach maximum condensation and align along the cell's equatorial plane, known as the metaphase plate, pulled by spindle fibers attached to each chromosome's centromere. This precise alignment ensures that when sister chromatids separate, each daughter cell receives exactly one copy of every chromosome. Metaphase is used in karyotyping because chromosomes are most visible and identifiable at this stage.
Telophase
Telophase is the final stage of nuclear division in which two sets of chromosomes arrive at opposite poles of the cell and nuclear envelopes reform around each set. Chromosomes begin to decondense back into chromatin, the spindle apparatus disassembles, and nucleoli reappear in the new nuclei. Telophase is immediately followed by cytokinesis, which divides the cytoplasm to complete the formation of two daughter cells.
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.
From Greek "ana" meaning up or back and "phasis" meaning appearance; the prefix "ana" conveys the movement of chromosomes back toward the poles of the cell.