Anaphase


Anaphase

Anaphase, from the ancient Greek "ἀνά" (up) and "φάσις" (stage), is the stage of mitosis when chromosomes separate in a eukaryotic cell. Each chromatid moves to opposite poles of the cell, the opposite ends of the mitotic spindle, near the microtubule organizing centers. During this stage, anaphase lag could happen.

Regulation

Anaphase begins abruptly with the regulated triggering of the metaphase-to-anaphase transition. At this point the Anaphase Promoting Complex (APC) becomes activated. This terminates metaphase (M-phase) activity by cleaving and inactivating the M-phase cyclin required for the function of M-phase cyclin dependent kinases (M-Cdks). It also cleaves securin, a protein that inhibits the protease known as separase. Separase then cleaves cohesin, a protein responsible for holding sister chromatids together.

Early and late anaphase

Within anaphase two distinct processes occur.

* During early anaphase (or Anaphase A) the chromatids abruptly separate and move towards the spindle poles. This is achieved by shortening of the spindle microtubules, and forces are mainly exerted at the kinetochores.

* When the chromatids are fully separated late anaphase (or Anaphase B) begins. This involves the polar microtubules elongating and sliding relative to each other to drive the spindle poles further apart. Anaphase B drives separation of the sister centrosomes to their opposite poles through three forces. Kinesin proteins attached to polar microtubules push the microtubules past one another. A second force involves pulling of the microtubules by cortex-associated cytosolic dynein. The third force for the separation of chromosomes involves lengthening the polar microtubules at the plus end.

These two processes were originally distinguished by their different sensitivities to drugs, and mechanically they are distinct processes.
* Early anaphase involves shortening kinetochore microtubules by depolymerization at both ends. During this, motor proteins at the kinetochores pull on the kinetochore microtubules.
* Late anaphase involves both the elongation of overlap microtubules and the use of two distinct sets of motor proteins: one of these pulls overlap microtubules past each other, the other pulls on astral microtubules that have attached to the cell cortex.

The contributions of early anaphase and late anaphase to anaphase as a whole vary with cell type. In mammalian cells, late anaphase follows shortly after early anaphase and extends the spindle to around twice its metaphase length; in contrast yeast and certain protozoa use late metaphase as the main means of chromosome separation and can extend the spindle to up to 15 times its metaphase length in the process.


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  • anaphase — [ anafaz ] n. f. • 1887; en all. 1884; de ana et phase ♦ Biol. Stade de la mitose, entre la métaphase et la télophase, au cours duquel les chromosomes divisés se séparent et migrent vers les deux pôles du fuseau. ● anaphase nom féminin Troisième… …   Encyclopédie Universelle

  • anaphase — n. 1. the stage of meiosis or mitosis when chromosomes move toward opposite ends of the nuclear spindle. [WordNet 1.5] …   The Collaborative International Dictionary of English

  • anaphase — anaphase. См. анафаза. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Anaphase — Anaphase, 3. Phase der ⇒ Mitose und der ⇒ Meiose …   Deutsch wörterbuch der biologie

  • anaphase — 1887, coined in German (1884), from Gk. ana (see ANA (Cf. ana )) + PHASE (Cf. phase) …   Etymology dictionary

  • anaphase — [an′ə fāz΄] n. [ ANA + PHASE1] Biol. the stage in mitosis, after the metaphase and before the telophase, in which the divided chromosomes move apart toward the poles of the spindle …   English World dictionary

  • Anaphase — Schematische Darstellung der Mitose I: Interphase; II: Prophase; III: Prometaphase; IV: Metaphase; V und VI: Anaphase; VII: Telophase; VIII: Zytokinese Als Mitose (zu griechisch μίτος = Faden) (auch Karyokinese) bezeichnet man den Vorgang der Z …   Deutsch Wikipedia

  • Anaphase — Schéma de l anaphase L anaphase est une phase très rapide de la méiose et de la mitose où les chromatides sœurs (durant la mitose) ou les chromosomes homologues (durant la méiose) se séparent et migrent vers les pôles opposés de la cellule.… …   Wikipédia en Français

  • anaphase — The stage of mitosis or meiosis in which the chromosomes move from the equatorial plate toward the poles of the cell. In mitosis a full set of daughter chromosomes (46 in humans) moves toward each pole. In the first division of meiosis one …   Medical dictionary

  • anaphase — n. the third stage of mitosis and of each division of meiosis. In mitosis and anaphase II of meiosis the chromatids separate, becoming daughter chromosomes, and move apart along the spindle fibres towards opposite ends of the cell. In anaphase I… …   The new mediacal dictionary


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